Slide 1

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 2

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 3

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 4

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 5

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 6

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 7

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 8

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 9

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 10

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 11

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 12

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 13

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 14

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 15

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 16

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 17

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 18

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 19

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 20

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 21

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 22

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 23

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 24

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 25

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 26

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 27

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 28

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 29

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 30

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 31

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 32

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 33

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 34

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 35

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 36

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 37

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 38

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 39

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 40

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 41

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 42

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 43

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 44

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 45

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 46

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 47

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 48

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 49

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 50

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 51

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 52

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 53

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 54

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 55

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 56

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 57

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 58

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 59

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 60

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 61

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 62

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 63

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 64

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 65

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 66

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 67

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 68

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 69

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 70

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 71

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 72

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 73

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 74

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 75

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 76

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.


Slide 77

Lesson 7
2014

Lesson 7
2014

 Our goal is, that after this lesson, students

are able to recognize the key criteria for
selecting composites and are able to use this
knowledge to support the systematic
material selection process.

Composites
Advantages

Disadvantages

 Typically the strength of the

 Recycling is necessary due to

material is increased
 Light weight constructions
 80% lighter than steel
 60% lighter than aluminium

 Also other properties than

strength could be tuned
according to the requirements:
 Rigidity vs. elasticity
 Thermal and electrical

properties
 Corrosion resistance

”too high” lifetime
 Some raw materials and
manufacturing methods are
expensive
 Some manufacturing methods
suffer from poor energy
efficiency
 Strength analysis are usually
challenging due to anisotropic
structure of many composites

Outline
 1 Definitions and composite types
 2 Basic composite theory
 3 Materials used in composites

 4 Tools to support systematic selection of composites
 5 Applications of composites

Composition

+
MATRIX

=

REINFORCEMENT

COMPOSITE

How to define, what is a real
composite?
MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B

1+1=2
MATERIAL ALLOY

MATERIAL 1
PROPERTIES A

+

MATERIAL 2
PROPERTIES B

=

NEW MATERIAL
PROPERTIES A+B
+ ADDED VALUE!

1+1>2
COMPOSITE MATERIAL

Composite types
DIFFERENT
STRUCTURES

Mixed materials
Added fibres
Sandwich-structures
Cell-structures

DIFFERENT
SCALES

Continuous fibres
Particles
Nanoparticles

DIFFERENT
MATERIALS

Matrix
Reinforcement
Alloys/Compounds

Theory of fibre-reinforced composites
 Fibres are typically used to improve composite’s strength,

rigidity and fatigue resistance.
 The matrix conveys the affecting load to be carried by the
fibres.
 Typically fibre-reinforced composites can withstand better
tensile loads than compression.
 The direction, length, density and cross-section’s shape
and area of the fibres can be tuned to produce the required
material properties.

TYPES OF FIBRE-REINFORCED MATERIALS

A

B

C

CONTINUOUS FIBREREINFORCED MATERIAL
- Direction can be tuned

SHORT FIBRE-REINFORCED
MATERIAL
- Length and direction can be tuned

WOVEN FIBRE-REINFORCED
- Direction and density can be tuned

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F

F

F

F

F

F

MATRIX
FIBRE

HIGH MODULUS OF
ELASTICITY

LOW MODULUS OF ELASTICITY

IMPORTANCE OF FIBRE DIRECTION COMPARED TO LOADING
F
F

F

F

F

F

F

HIGH MODULUS OF ELASTICITY
LOW MODULUS OF ELASTICITY

F

F

Ultimate tensile strength

F

IMPORTANCE OF FIBRE DIRECTION
COMPARED TO LOADING

F

F

0°
30° 45° 60°
90°
The angle between the directions of the affecting
load and reinforcing fibres [°]

Finally: the composite breaks when also the
matrix breaks down.

When fibres break, the strength of the composite
decreases to the level of matrix’s yeld strength.

The matrix yelds and the composite’s modulus of
elasticity decreases. The additional load is
carried by the fibres with elastic elongation.

Elastic elongation of the composite. The value of
the modulus of elasticity is stable.

STRESS-STRAIN-CURVE OF A FIBRE COMPOSITE
STRESS

σ

σcr

σc

σm
STRAIN

ε

BORON NITRIDE
5 µm

CARBON FIBRES
5-7 µm

GLASS FIBRES
10 µm

METAL WIRES
25 µm

COATED
FIBRES:
BORON
CARBIDE
SILICON
CARBIDE
130 µm

CROSS-SECTION AREAS OF DIFFERENT FIBRES

THE ”VISION” OF 3D-WOVEN FIBRE-REINFORCEMENT

“THE RULE OF MIXTURES:”

 The strain of the composite is equal to the mean value

of strains of each material of the composite, if the
strain magnitudes of each material of the composite
are weighted by their percentage of composite volume.
 The modulus of the elasticity can be determined with
an analogic way.

 By applying the rule of mixtures the modulus of

elasticity of the fibre reinforced composite is (two
values are needed due to the anisotropic structure):

•

In which:
– Vf fibres’ percentage of the total composite volume
– Ef modulus of elasticity of the fibres
– Em modulus of elasticity of the matrix
– Ec modulus of elasticity of the composite

GRAPHIC INTERPRETATION OF THE RULE OF MIXTURES
Stress
σ1

Fibre Ef=σ1/ε

σ2

Composite Ec=σ2/ε
(e.g.70% portion of
fibres)

σ3

Matrix Em=σ3/ε
ε
Strain

DUCTILITY OF FIBRE-REINFORCED COMPOSITES

 Usually the ductility of fibre-reinforced

composites does NOT refer to elongation to
break
BUT
 it describes the ability of the composite to
absorb the damaging energy, which could
cause the crack growth in the composite.
 Usually the most important characteristic to
describe this ability is the bonding strength
between the fibre and matrix.

Fixed end of the fibre
Fallowed=σcontact area×π×D×L

FRACTURE IN THE MATRIX

MATRIX

ØD
FIBRE

L

The empty space due to
the loosen end of the fibre

Theory of particle reinforced composites
 Particle reinforced composites have mostly
isotropic material properties.
 Based on the size of the alloyed particles two types
of composites are available:
 Particle reinforced composites
 Dispersion reinforced particle composites
 Dispersion reinforced particle composites have
usually better strength properties due to evenly
distributed particle amount inside the whole
matrix

 By applying the rule of mixtures the modulus of
elasticity of the fibre reinforced composite is :

 In theory the exponent ”n” gets the value of ”1” if
the structure is like ”rubber particles in steel
matrix”.
 In theory the exponent ”n” gets the value of ”-1” if
the structure is like ”steel particles in rubber
matrix”.
 The real values of exponent ”n” are between -1…1.

Theory of laminate composites
 Three basic variations of layered composites are
available:
 Construction based on different directions of

fibres in laminate’s layers
 Construction based on different material layers
 Combination of the previous two constructions

LAMINATE COMPOSITE

90°

0°

-45°

+45°

90°

0°

Example of a laminate
composite structure

LAMINATE COMPOSITE

In one direction reinforced
aramid fibre polymer matrix
composite

Aluminium plate

Theory of sandwich composites
 In most of cases the question is more about
sandwich constructions than composite materials.
 Composite materials can be utilized as parts of
sandwich structures.
 Usually the rigidity of the construction is tuned by
utilizing special core constructions in layered
applications.
 The final strength and rigidity is achieved by
combining the different layers and the core
construction.

Coating
Load bearing plate

Fixing layer

A COMPOSITE
MATERIAL
OR

Honeycomb

A CONSTRUCTION

Fixing layer

?

Load bearing plate
Coating

PRINCIPLE OF THE HONEYCOMB STRUCTURE

DIFFERENT SHAPES AND SIZES OF THE HONEYCOMB STRUCTURE

Theory of cell structure composites
 Typically the properties of cell structure
composites depend on:
 density ratio between the whole cell structure
and the wall material of the cells
 the selected cell structure type: open cells or
closed cells
 the filler material of the cell (in many cases it is
air).

 The modulus of elasticity of cell structure composites can be estimated

with the equation:







In which:
Ecs =modulus of the elasticity of the cell structure composite
Ρ = density of the cell structure composite (of the ”foam”)
Esm = modulus of the elasticity of the wall material
ρsm = density of the wall material

 The density ratio ρ/ρsm of the most common cell structure

constructions can vary between 0,5 – 0,005, which means that with the
same wall material the modulus of elasticity of the cell structure
composite can have the ratio up to 1/10 000.

COMPRESSION STRESS

CELL STRUCTURE COMPOSITES

In the beginning
there is the area,
where the walls of
the cell composite
bend in an elasticlinear way.

Deformation increases while
the stress remains almost
stable. Cell walls suffer from
buckling.

DEFORMATION (COMPRESSION)

Cell structure starts
to behave like the
pure wall material of
the composite,
because the walls
have compressed
against each other.

Viewpoints of strength analysis
 Fibre reinforced composites have anisotropic material







properties (also fibre reinforced MMC composites!).
Anisotropic behaviour is relevant for strength, heat
expansion and heat conductivity properties.
Some manufacturing technologies can cause anisotropic
properties also to particle reinforced composites (e.g. some
extrusion technologies).
Stress-strain behaviour is non-linear.
Particle reinforced composites and MMC composites might
suffer from brittle behaviour.
Due to anisotropic properties many composites suffer from
internal stresses, which are hard to estimate, but which
should be taken into account in strength analysis.
Joining technology of composite components requires
special attention.

Composite materials
METALS

METALS

POLYMERS

POLYMERS

CERAMICS

CERAMICS

Family of composites
POLYMERS
FIBRES

METALS

POLYMER
MATRIX
COMPOSITES

FIBRE
REINFORCED
COMPOSITES

METAL
MATRIX
COMPOSITES

FAMILY OF
COMPOSITES

CERAMICS

CERAMIC
COMPOSITES

NANOMATERIALS
NANOCOMPOSITES

ADAPTIVE
MATERIALS

The most common composites
 Metal Matrix Composites (MMC)
 Increasingly found in the automotive industry.
 These materials use a metal such as aluminium as the matrix, and

reinforce it with fibres such as silicon carbide.

 Polymer Matrix Composites (PMC)
 Also known as FRP - Fibre Reinforced Polymers (or Plastics).
 These materials use a polymer-based resin as the matrix, and a variety

of fibres such as glass, carbon and aramid as the reinforcement.

 Ceramic Matrix Composites (CMC)
 Used in very high temperature environments.
 These materials use a ceramic as the matrix and reinforce it with short

fibres, or whiskers such as those made from silicon carbide and boron
nitride.

What do we know already?
POLYMERS

- TEMPERATURE RELATED CHARACTERISTICS
- ASPECTS OF CHEMISTRY (POLYMER CHAIN)
- CREEPING STERNGTH, VISCOELASTICITY

POLYMER
MATRIX
COMPOSITES

CERAMICS
CERAMIC
COMPOSITES

METALS
METAL
MATRIX
COMPOSITES

- POWDER METALURCICAL PROCESS
- IMPORTANCE OF SINTERING AND
COMPRESSION DIRECTION
- PURITY LEVEL, POROSITY, GRAIN SIZE
- ALLOYING (ZrO2 / BRITTLENESS)

- PRESSURE CASTING PROCESSES
- POWDER METALLURGICAL PROCESS
- IMPORTANCE OF ALLOYING

 Examples of fibre reinforced constructional composites:
 Fibre / Polymer matrix
 Kevlar / epoksi

 C (graphite) / PEEK
 C (graphite) / PPS

 Fibre / Metal matrix
 SiC / Al
 SiC / Ti

 Fibre / Ceramic matrix
 C / SiC

 SiC / Si3N4

CLASSIFICATION OF FIBRE REINFORCEMENTS
Glass fibres

Inorganic

Carbon fibres

REINFORCEMENT FIBRES

Basalt fibres

SYNTHETIC
Polymers

Organic
Cellulose fibres

Mineral fibres

BIOFIBRES

Asbestos

Animal fibres
Wood fibres

Vegetation fibres

Hemp fibres
Flax fibres
Bamboo fibres

Aramid fibres
(Kevlar)

Metal matrix composites (MMC)
MMC
TYPES

FIBER
COMPOSITES

PARTICLE
COMPOSITES

LAYER
COMPOSITES

Continuous fibers, discontinuous fibers, whiskers, particlers, wires

Metal matrix composites (MMC)
MMC
MANUFACTURING

Melting
metallurgical
processes
Pressure casting
infiltration of metallic
matrix between long or
short fiber or particle
reinforcement nets.

Powder
metallurgical
processes
Pressing and sintering
composite powders or
extrusion of metalpowder particle
composites

Pressing
processes

Hot isostatic
pressing of
powder mixtures
and fibers

Pressure casting infiltration

PROCESS PROGRESS

The most important MMC’s


Aluminum matrix







Magnesium matrix






Continuous fibers: silicon carbide, coated boron
Particles: titanium carbide

Copper matrix






Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide

Titanium matrix





Continuous fibers: boron, silicon carbide, alumina, graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particles: silicon carbide, boron carbide

Continuous fibers: graphite, silicon carbide
Wires: niobium-titanium, niobium-tin
Particles silicon carbide, boron carbide, titanium carbide.

Superalloy matrices


Wires: tungsten

MMC’s compared to metals
 Higher strength-to-density ratio
 Higher stiffness-to-density ratio
 Better fatigue resistance

 Higher strength in elevated temperatures
 Lower coefficients of thermal expansion
 Better wear resistance

MMC’s compared to PMC’s
 Higher temperature capability
 (Better) fire resistance
 Higher transverse stiffness and strength

 No moisture absorption
 Higher electrical and thermal conductivities
 Better radiation resistance

Polymer Matrix Composites (PMC)
 Two types of polymers are used as matrix materials:
 Thermosets (epoxies, phenolics)
 Thermoplastics (Low Density Polyethylene LDPE, High Density
Polyethylene HDPE, polypropylene, nylon, acrylics).
 According to the reinforcement material the following

groups of Polymer Matrix Composites (PMC) are used:
 Fibre glasses – Glass Fibre Reinforced Polymer Composites
 Carbon Fibre Reinforced Polymer Composites
 Kevlar (Aramid) Fibre Reinforced Polymer Composites.

 Properties of Polymer Matrix Composites are determined by the

earlier presented theory of fibre reinforced composites.

Polymer Matrix Composites (PMC)
 By fibre reinforced structures the properties of

ordinary polymers can be improved remarkably
(strength, stiffness, abrasion resistance, toughness
etc.)
 PMC’s have low material and manufacturing costs
compared to other composite materials.
 The main disadvantages of Polymer Matrix
Composites are:
 Low thermal resistance
 High coefficient of thermal expansion.

Fibre comparison for PMC’s
Property

Range 1..3, 1=best

Fibre material
Kevlar

Carbon

Glass

High tensile strength

2

1

2

High compression strength

3

1

2

High modulus of elasticity

2

1

3

Impact strength

1

3

2

Low density

1

2

3

Good fire resistance

1

3

1

Low thermal expansion

1

1

1

Low cost

3

3

1

Ceramic Matrix Composites (CMC)
 Examples of ceramic matrices include Al2O3 , Al2Ti5,

AlN, TiN, ZrN, TiC, and ZrC.
 Most typical CMC systems are:
 C / SiC
 SiC / Si3N4

 Although developed initially to reinforce aluminum

and titanium matrices (MMC), SiC filaments have
been used as reinforcement in silicon nitride.

Development steps of CMC’s
 Ways to control the bond between the matrix and the







reinforcement : boron nitride (BN) and carbon
Ways to increase the fracture toughness of the
composite: thermal treatments or CVD coatings of the
fibers before their incorporation into an Al2O3 matrix
Ways to develop fibres, which are stable in oxidizing
environments (after the possible matrix failure when the
reinforcement fiber has air contact).
Ways to develop damage-tolerant and ductile ceramicceramic composites.
Ways to develop high-temperature reinforcements for
ceramic-ceramic composites (utilization of silicon carbide
SiC reinforcements)

PROPERTY MAPS

+

Polymer matrix
composites

Strength

Titanium matrix
composites
Titanium alloys
Ni/Co-alloys
Ceramic matrix
composites

_
_

Temperature

+

PROPERTY MAPS CONNECTED WITH COSTS

+

RECYCLABILITY

Metals and
metal alloys

Polymers

_

Traditional
composites

Ceramics
Biocomposites

_

COSTS

+

PROPERTY MAPS WITH PROPERTY RATIOS
METALS AND METAL ALLOYS

+
Modulus of elasticity/weight -ratio

CERAMICS
COMPOSITES
POLYMERS

_
_

Strength/weight -ratio

+

PROPERTY CURVES WITH PROPERTY RATIOS
Kevlar-fibres in the
epoxy-matrix
Metals
Glass fibres

Polymers

Boron-fibres
in the
aluminiummatrix

Garbonfibres in the
magnesium
-matrix

CARBONFIBRE
LAMINATE COMPOSITE

CARBONFIBRE SANDWICH
COMPOSITE

STEEL/
TITANIUM

ALUMINIUM

CARBONFIBRE SANDWICH
COMPOSITE

GLASSFIBRE
COMPOSITE

ROTOR BLADE CONNECTION
FRP COMPOSITE
ROTOR BLADES
FRP COMPOSITE

F1-car’s ”nose”
- polyamide/carbon
fibre composite

F1-car’s safety body ”the monocoque”
- carbon fibre composite
- carbon fibre/aluminium laminate structure
- Honeycomb-sandwich-structure

Wind wings and
vanes and other
aero detailed
parts
- kevlar- coating

F1-car’s brake disks
- carbon fibre/graphite (c/c)
- composite

 CASE: F1 Front Nose - Aerodynamic application for F1

wind tunnel, positioned on the front of an F1 car and
supporting the front wing (and so called “Nose” of an F1
car).
 The required base properties are:
 dimensional accuracy and detail definition
 the best compromise between stiffness and resistance
to vibration.
 Class of material
 Polyamide (PA) and Carbon based Composite Material
 Manufacturing Technology
 Selective Laser Sintering

 CASE: A construction material for Formula 1 cars, “The monocoque”
 could be made of epoxy resin reinforced with carbon fibre
 Manufacturing: laminated together
 Requirements: great rigidity and strength, but very lightweight

 Notice from the table that carbon fibres are 3 times stronger and more than 4
times lighter than steels.

Tensile
strength

Density

Carbon
fibre

3.50

1.75

Steel

1.30

7.90

 CASE: The carbon brake discs used in Formula 1
 Requirements:
 May not be thicker than 28 millimetres and their diameter may not exceed

278 millimetres.
 When braking, the discs heat up to as much as 600…1000 degrees Celsius
within one second
 Full braking will bring a Formula 1 car from 200 to 0 km/h within 55
metres, all within 1.9 seconds. Deceleration forces achieve up to 5 G
 Material: carbon-carbon composite (Carbon fibre-reinforced Carbon
(carbon-carbon, C/C) is a composite material consisting of carbon fiber
reinforcement in a matrix of graphite

 Properties: Composite brake discs are used instead of steel or cast iron

because of their

 superior frictional, thermal, and anti-warping properties,
 as well as significant weight savings.

 CASE: To avoid sharp carbon fibre splinters on the track

after accidents, all front wings, barge boards and small
aerodynamic body parts must be given an additional outer
coating of Kevlar® (or a similar type of material).

Metal Matrix composites (MMC)
E.g 75% high-strength Al-Cu alloy (AA-2124) + 25% SiC

 Typical low cost body armor systems utilize Aramid

fibers while Kevlar is used in cost-effective high
performance systems.