Transcript High-Performance Composites

Textile Structural Composites
Yiping Qiu
College of Textiles
Donghua University
Spring, 2006
Reading Assignment



Textbook chapter 1 General Information.
High-Performance Composites: An Overview,
High-Performance Composites, 7-19, 2003
Sourcebook.
FRP Materials, Manufacturing Methods and
Markets, Composites Technology, Vol. 6(3) 6-20,
2000.
Expectations

At the conclusion of this section, you should be
able to:



Describe the advantages and disadvantages of fiber
reinforced composite materials vs. other materials
Describe the major applications of fiber reinforced
composites
Classification of composites
Introduction

What is a composite material?


Why composite materials?



Two or more phases with different properties
Synergy
History
Current Status
Introduction

Applications





Automotive
Marine
Civil engineering
Space, aircraft and military
Sports
Applications in plane
Fiber reinforced composite materials

Classifications according to:

Matrices




Polymer
 Thermoplastic
 Thermoset
Metal
Ceramic
Others
Fiber reinforced composite materials

Classifications

Fibers



Length
 short fiber reinforced
 continuous fiber reinforced
Composition
 Single fiber type
 Hybrid
Mechanical properties


Conventional
Flexible
Fiber reinforced composite materials

Advantages
High strength to weight ratio
 High stiffness to weight ratio
 High fatigue resistance
 No catastrophic failure
 Low thermal expansion in fiber oriented
directions
 Resistance to chemicals and environmental
factors

0
materials
Kevlar/epoxy
Carbon/epoxy
Ti alloy
Al alloy
Steel
Specific gravity
(g/cc)
Comparison of specific gravities
8
6
4
2
0
Materials
Kevlar/epoxy
Carbon/epoxy
Ti alloy
Al alloy
Steel
Tensile strength (M Pa)
Comparison of tensile strength
1400
1200
1000
800
600
400
200
0
Materials
Kevlar/epoxy
Carbon/epoxy
Ti alloy
Al alloy
Steel
ratio (109m)
Modulus to weight
Comparison of modulus to
weight ratio
16
12
8
4
Fiber reinforced composite materials

Disadvantages
Good properties in one direction and poor
properties in other directions.
 High cost due to expensive material and
complicated fabrication processes.
 Some are brittle, such as carbon fiber reinforced
composites.
 Not enough data for safety criteria.

Design of Composite Materials


Property Maps
Merit index
Design of Composite Materials


Merit index
Example for tensile stiffness of a beam
W  V  AL
W W


when L  1
AL A

However, for a given tensile sample, tensile stiffness
has nothing to do with length or L = 1 may be
assumed

F
F
F
E  


 A W   W
E
F
 
 W
Design of Composite Materials

How about for torsion beams and bending
plates? Lets make the derivation of these
our first homework.
Major components for fiber-reinforced
composites

Reading assignment:


Fibers


Textbook Chapter 2 Fibers and matrices
Share major portion of the load
Matrix



To transfer stress between the fibers
To provide a barrier against an adverse environment
To protect the surface of the fibers from mechanical
abrasion
Major components for fiber reinforced
composites

Coupling agents and coatings



to improve the adhesion between the fiber and the matrix
to protect fiber from being reacted with the matrix or other
environmental conditions such as water moisture and
reactive fluids.
Fillers and other additives:





to reduce the cost,
to increase stiffness,
to reduce shrinkage,
to control viscosity,
to produce smoother surface.
Materials for fiber reinforced composites
Mainly two components:


Fibers
Matrices
Materials for fiber reinforced composites

Fibers

Influences:





Specific gravity,
Tensile and compressive strength and
modulus,
Fatigue properties,
Electrical and thermal properties,
Cost.
Materials for fiber reinforced composites

Fibers

Fibers used in composites

Polymeric fibers such as




PE (Spectra 900, 1000)
PPTA: Poly(para-phenylene terephthalamide) (Kevlar
29, 49, 149, 981, Twaron)
Polyester (Vectran or Vectra)
PBZT: Poly(p-phenylene benzobisthiozol)
Materials for fiber reinforced composites

Fibers

Inorganic fibers:




Glass fibers: S-glass and E-glass
Carbon or graphite fibers: from PAN and Pitch
Ceramic fibers: Boron, SiC, Al2O3
Metal fibers: steel, alloys of W, Ti, Ni, Mo etc.
(high melting temperature metal fibers)
Materials for fiber reinforced composites

Most frequently used fibers





Glass
Carbon/graphite
PPTA (Kevlar, etc.)
Polyethylene (Spectra)
Polyester (Vectra)
Materials for fiber reinforced composites

Carbon fibers


Manufacturing processes
Structure and properties
Materials for fiber reinforced composites

Carbon fibers

Manufacturing processes

Thermal decomposition of fibrous organic
precursors:


PAN and Rayon
Extrusion of pitch fibers
Materials for fiber reinforced composites

Carbon fiber manufacturing processes

Thermal decomposition of fibrous organic
precursors

Rayon fibers
 Rayon based carbon fibers
 Stabilization at 400°C in O2, depolymerization &
aromatization
 Carbonization at 400-700°C in an inert atmosphere
 Stretch and graphitization at 700-2800°C (improve
orientation and increase crystallinity by 30-50%)
Materials for fiber reinforced composites

Carbon fiber manufacturing processes

Thermal decomposition of fibrous organic
precursors

PAN (polyarylonitrile) based carbon fibers

PAN fibers (CH2-CH(CN))
 Stabilization at 200-300°C in O2, depolymerization &
aromatization, converting thermoplastic PAN to a nonplastic
cyclic or ladder compound (CN groups combined and CH2
groups oxidized)
 Carbonization at 1000-1500°C in an inert atmosphere to get rid
of noncarbon elements (O and N) but the molecular orientation is
still poor.
 Stretch and graphitization at >1800°C, formation of turbostratic
structure
Materials for fiber reinforced composites

Pitch based carbon fibers




pitch - high molecular weight byproduct
of distillation of petroleum
heated >350°C, condensation reaction,
formation of mesophase (LC)
melt spinning into pitch fibers
conversion into graphite fibers at
~2000°C
Materials for fiber reinforced composites

Carbon fibers

Advantages
High strength
 Higher modulus
 Nonreactive





Resistance to corrosion
High heat resistance
high tensile strength at elevated temperature
Low density
Materials for fiber reinforced composites

Carbon fibers

Disadvantages
High cost
 Brittle

Materials for fiber reinforced composites

Carbon fibers

Other interesting properties
Lubricating properties
 Electrical conductivity
 Thermal conductivity
 Low to negative thermal expansion coefficient

Materials for fiber reinforced composites

Carbon fibers

heat treatment below 1700°C
less
crystalline
and lower modulus (<365 GPa)

Graphite fibers

heat treatment above 1700°C
More
crystalline (~80%) and
higher modulus (>365GPa)
Materials for fiber reinforced composites

Glass fibers


Compositions and properties
Advantages and disadvantages
Materials for fiber reinforced composites

Glass fibers

Compositions and Structures


Mainly SiO2 +oxides of Ca, B, Na, Fe, Al
Highly cross-linked polymer




Noncrystaline
No orientation
Si and O form tetrahedra with Si centered and O at the
corners forming a rigid network
Addition of Ca, Na, & K with low valency breaks up the
network by forming ionic bonds with O   strength
and modulus
Microscopic view of glass fiber
Cross polar
First order red plate
Materials for fiber reinforced composites

Glass fibers

Types and Properties

E-glass (for electric)



draws well
good strength & stiffness
good electrical and weathering properties
Materials for fiber reinforced composites

Glass fibers

Types and Properties

C-glass (for corrosion)


good resistance to corrosion
low strength
Materials for fiber reinforced composites

Glass fibers

Types and Properties

S-glass (for strength)



high strength & modulus
high temperature resistance
more expensive than E
Materials for fiber reinforced composites

Properties of Glass fibers
fibers
Tensile
strength
(MPa)
Tensile
Modulus
(GPa)
Dielectric
Const. (a)
72.5
Coeff. Of
Thermal
Expension
10-6/K
5.0
E-glass
3450
S-glass
4590
86.0
5.6
5.1
6.3
Materials for fiber reinforced composites

Glass fibers

Production

Melt spinning
Materials for fiber reinforced composites

Glass fibers

sizing:

purposes





protest surface
bond fibers together
anti-static
improve interfacial bonding
Necessary constituents



a film-forming polymer to provide protecting
 e.g. polyvinyl acetate
a lubricant
a coupling agent: e.g. organosilane
Materials for fiber reinforced composites

Glass fibers

Advantages
high strength
 same strength and modulus in transverse direction
as in longitudinal direction
 low cost

Materials for fiber reinforced composites

Glass fibers

disadvantages
relatively low modulus
 high specific density (2.62 g/cc)
 moisture sensitive

Materials for fiber reinforced composites

Kevlar fibers

Structure
Polyamide with benzene rings between amide
groups
 Liquid crystalline
 Planar array and pleated system

Materials for fiber reinforced composites

Kevlar fibers

Types
Kevlar 29, E = 50 GPa
 Kevlar 49, E = 125 GPa
 Kevlar 149, E = 185 GPa

Materials for fiber reinforced composites

Kevlar fibers

Advantages
high strength & modulus
 low specific density (1.47g/cc)
 relatively high temperature resistance

Materials for fiber reinforced composites

Kevlar fibers

Disadvantages
Easy to fibrillate
 poor transverse properties
 susceptible to abrasion

Materials for fiber reinforced composites

Spectra fibers

Structure: (CH2CH2)n
Linear polymer - easy to pack
 No reactive groups


Advantages
high strength and modulus
 low specific gravity
 excellent resistance to chemicals
 nontoxic for biomedical
applications

Materials for fiber reinforced composites

Spectra fibers

Disadvantages
poor adhesion to matrix
 high creep
 low melting temperature

Materials for fiber reinforced composites

Other fibers

SiC and Boron

Production

Chemical Vapor Deposition (CVD)
 Monofilament
 Carbon or Tungsten core heated by passing an
electrical current
 Gaseous carbon containing silane
Materials for fiber reinforced composites

SiC

Production


Polycarbosilane (PCS)
 Multi-filaments
 polymerization process to produce precursor
 PCS pyrolised at 1300ºC
Whiskers
 Small defect free single crystal
Materials for fiber reinforced composites

Particulate



small aspect ratio
high strength and modulus
mostly cheap
Materials for fiber reinforced composites

The strength of reinforcements



Compressive strength
Fiber fracture and flexibility
Statistical treatment of fiber strength
Materials for fiber reinforced composites

The strength of reinforcements

Compressive strength

(Mainly) Euler Buckling
EI
Pc 2
L
 *b 
 Ed
2
 
16  L 
2
Materials for fiber reinforced composites

The strength of reinforcements

Factors determining compressive strength
Matrix material
 Fiber diameter or aspect ratio (L/d)
 fiber properties


carbon & glass >> Kevlar
Materials for fiber reinforced composites

The strength of reinforcements

Fiber fracture

Mostly brittle


Some ductile


e.g. Carbon, glass, SiC
e.g. Kevlar, Spectra
Fibrillation

e.g. Kevlar
Materials for fiber reinforced composites

The strength of reinforcements

Fiber flexibility
How

easy to be bent
Moment required to bend a round fiber:
M  EI  E
d
64
E = Young’s Modulus
d = fiber diameter
 = curvature
4

Materials for fiber reinforced composites

The strength of reinforcements

Fiber failure in bending
Stress

on surface
Tensile stress:
Ed

2
E = Young’s Modulus
d = fiber diameter
 = curvature
Materials for fiber reinforced composites

The strength of reinforcements

Fiber failure in bending
Stress

on surface
Maximum curvature
 max
2 *

Ed
* = fiber tensile strength
Materials for fiber reinforced composites

The strength of reinforcements

Fiber failure in bending
When
bent, many fibers fail in compression
Kevlar forms kink bands
Materials for fiber reinforced composites

Statistical treatment of fiber strength

Brittle materials: failure caused by random
flaw
don’t
have a well defined tensile strength
presence of a flaw population

Statistical treatment of fiber strength
Peirce
(1928): divide a fiber into incremental
lengths
L  L1  L2  L3   LN
Materials for fiber reinforced composites

Statistical treatment of fiber strength

Peirce’s experiment

Hypothesis:
The longer the fiber length, the higher the probability
that it will contain a serious flaw.
 Longer fibers have lower mean tensile strength.
 Longer fibers have smaller variation in tensile strength.

Materials for fiber reinforced composites

Statistical treatment of fiber strength

Peirce’s experiment

Experimental verification:
 nl /  l  1  4.2(1  n 1/ 5 )CV
 nl  Strengthof fiber with a lengthof nl
 l  Strengthof fiber with a lengthof l
CV  Coefficient of variation
Materials for fiber reinforced composites

Statistical treatment of fiber strength

Weakest Link Theory (WLT)
define
n = No. of flaws per unit length causing
failure under stress .
For the first element, the probability of failure
Pf 1  n L1
The probability for the fiber to survive
Ps  (1  Pf 1 )(1  Pf 2 )(1  PfN )
Materials for fiber reinforced composites

Statistical treatment of fiber strength

Weakest Link Theory (WLT)
If
the length of each segment is very small, then
Pfi are all very small,

Therefore (1-Pfi)  exp(-Pfi)
The
probability for the fiber to survive
Ps  exp[( Pf 1  Pf 2   PfN )]
 exp[(n L1  n L2   n LN )]  exp(Ln )
Materials for fiber reinforced composites

Statistical treatment of fiber strength

Weibull distribution of fiber strength
Weibull’s
assumption:

L0 n  
0



m
m = Weibull shape parameter (modulus).
0 = Weibull scale parameter, characteristic
strength.
L0 = Arbitrary reference length.
Materials for fiber reinforced composites

Statistical treatment of fiber strength

Weibull distribution of fiber strength
Thus
  L
Pf  1  exp 
  L0
 

  0



m



Materials for fiber reinforced composites

Statistical treatment of fiber strength

Weibull distribution of fiber strength
Discussion:
Shape parameter ranges 2-20 for ceramic and many
other fibers.
 The higher the shape parameter, the smaller the
variation.
 When  <0, the probability of failure is small if m is
large.
 When  0, failure occurs.
 Weibull distribution is used in bundle theory to predict
fiber bundle and composite strength.

Materials for fiber reinforced composites

Statistical treatment of fiber strength

Weibull distribution of fiber strength

Plot of fiber strength or failure strain data

let
 L   
ln(Ps )    
 L0   0 
 1   L   
ln     
 Ps   L0   0 
m
m
  1 
ln ln   lnL   lnL0   m ln   m ln 0 
  Ps 
Statistical treatment of fiber strength

Example


Estimate number of fibers fail at a gage
length twice as much as the gage length in
single fiber test
L/L0 = 2
Matrices

Additional reading assignment:

Jones, F.R., Handbook of PolymerFiber Composites, sections:

2.4-2.6, 2.9, 2.10, 2.12.
Matrices



Polymer
Metal
Ceramic
Matrices

Polymer

Thermosetting resins




Epoxy
Unsatulated polyester
Vinyl ester
high temperature:
 Polyimides
 Phenolic resins
Matrices
Polymer
Target net resin properties
Properties
minimum
desired
Typical
epoxy
Tensile strength
(MPa)
Modulus (GPa)
70
>100
---
2.0
>3.0
3.8
Ultimate Strain
(%)
Glass transition
temperature (C)
5
>10
1-2
121
>177
121
Epoxy resins

Starting materials:

Low molecular weight organic compounds
containing epoxide groups
Epoxy Resins

Types of epoxy
resins
Epoxy resins

Types of epoxy resin

bifuctional: diglycidyl ether of bisphenol A


a distribution of monomers  n is fractional:
effect of n
  molecular weight   viscosity   curing temp.
  distance between crosslinks   Tg &  ductility
  -OH  moisture absorption
Epoxy resins

Types of epoxy resin (cont.)
Trifunctional (glycidyl amines)
 Tetrafunctional





higher functionality
potentially higher crosslink densities
higher Tg
Less -OH groups   moisture absorption
Epoxy resins

Curing

Copolymerization:





A hardener required: e.g. DDS, DICY
Hardeners have two active “H” atoms to add to the epoxy
groups of neighboring epoxy molecules, usually from NH2
Formation of -OH groups: moisture sensitive
Addition polymerization: No small molecules formed 
no volatile formation
Stoichiometric concentration used, phr: part per hundred
(parts) of resin
Epoxy resin

Major ingredients: epoxy resin and curing
agent
Epoxy resin

Chemical reactions
Epoxy resin

Chemical reactions
Epoxy resins

Curing

Homopolymerization:




Addition polymerization: a catalyst or initiator required:
eg. Tertiary amines and BF3 compounds
Less -OH groups formed
Typical properties of addition polymers
Combination of catalyst with hardeners
Epoxy Resins

Reaction of homopolymerization
Epoxy resins

Epoxy resins

Mechanical and thermomechanical properties
Effect of curing agent on mechanical properties
 Heat distortion temperature (HDT)




measured as temperature at which deflection of 0.25 mm
of 100 mm long bar under 0.455 MPa fiber stress occurs.
related but  Tg
Moisture absorption: 1% decrease Tg by 20ºK
Polyimides

Largest class of high temperature polymers in
composites

Types

PMR (polymerization of monomeric reactants)



polyimides are insoluble and infusible.
in situ condensation polymerization of monomers in a solvent
2 stage process:


first stage to form imidized prepolymer of oligomer and volatile
by-products removed using autoclave or vacuum oven.
Second stage: prepolymer is crosslinked via reaction of the
norbornene end cap under high pressure and temperature (316ºC
and 200 psi)
Polyimides

Types
 bis-imides (derived from monomers with 2
preformed imide groups).


Typical BMI (bismaleimides)
Used for lower temperature range ~ 200ºC
Polyimides

Properties (show tables)
Polyimides

Advantages:


Heat resistant
Drawbacks:
toxicity of constituent chemicals (e.g. MDA)
 microcracking of fibers on thermal cycling
 high processing temperature


Typical Applications
 Engine
parts in aerospace industry
Phenolic resins


Prepared through condensation
polymerization between phenol and
formaldehyde.
Large quantity of Water generated (up to
25%) leading to high void content
Phenolic resins

Advantages:





High temperature stability
Chemical resistance
Flame retardant
Good electrical properties
Typical applications





Offshore structures
Civil engineering
Marine
Auto parts: water pumps, brake components
pan handles and electric meter cases
Time-temperature-transformation diagrams
for thermosets resins

Additional reading assignment:

reserved: Gillham, J.K., Formation and
Properties of Thermosetting and High Tg
Polymeric Materials, Polymer Engineering
and Science, 26, 1986, p1429-1431
Time-temperature-transformation diagrams
for thermosets resins
Time-temperature-transformation diagrams
for thermosets resins

Important concepts

Gelation
formation of an infinite network
 sol and gel coexist


Vitrification
Tg rises to isothermal temperature of cure
 Tcure > Tg, rubbery material
 Tcure < Tg, glassy material
 After vitrification, conversion of monomer
almost ceases.

Time-temperature-transformation diagrams
for thermosets resins

Important concepts

Devitrification
Tg decreases through isothermal temperature of
cure due to degradation
 degradation leads to decrosslink and formation of
plasticizing materials


Char or vitrification

due to increase of crosslink and volatilization of
low molecular weight plasticizing materials
Time-temperature-transformation diagrams
for thermosets resins

Important concepts

Three critical temperatures:
Tg - Tg of cured system
 gelTg - Tg of gel
 Tgo - Tg of reactants

Time-temperature-transformation diagrams
for thermosets resins

Discussion

Ungelled glassy state is good for
commercial molding compounds
Tgo > Tprocessing, processed as solid
 Tgo < Tprocessing, processed as liquid





Store temperature < gelTg to avoid gelation
Resin fully cured when Tg = Tg
Tg > Tcure about 40ºC
Full cure is achieved most readily by cure at
T > Tg and slowly at T < Tg.
Unsaturated polyester



Reading assignment
Mallick, P.K., Fiber Reinforced Composites .
Materials, Manufacturing and Design, pp56-64.
Resin:

Products of condensation polymerization of diacids and
diols



e.g. Maleic anhydride and ethylene glycol
Strictly alternating polymers of the type A-B-A-B-A-B
At least one of the monomers is ethylenically unsaturated
Unsaturated polyester
Unsaturated polyester
Unsaturated polyester

Cross-linking agent




Reactive solvent of the resin: e.g. styrene
Addition polymerization with the resin molecules:
initiator needed, e.g. peroxide
Application of heat to decompose the initiator to start
addition polymerization
an accelerator may be added to increase the
decomposition rate of the initiator.
Unsaturated polyester
Unsaturated polyester

Factors to control
properties

Cross-linking density:


addition of saturated diacids
as part of the monomer for
the resin: e.g phthalic
anhydrid, isophthalic acid
and terephthalic acid
as ratio of saturated acids to
unsaturated acids increases,
strength and elongation
increase while HDT
decreases
Unsaturated polyester

Factors controlling properties

Type of acids



Resin microstructure:


Terephthalic acids provide higher HDT than the other two acids
due to better packing of molecules
nonaromatic acid: adipic acid HOOC(CH2)4COOH, lowers
stiffness
local extremely high density of cross-links.
Type of diols


larger diol monomer: diethylene glycol
bulky side groups
Unsaturated polyester

Factors to control
properties

Type of crosslinking agent


amount of styrene: more
styrene increases the
distance of the space of
neighboring polyester
molecules  lower
modulus
Excessive styrene: selfpolymerization 
formation of polystyrene
 polystyrene-like
properties
Unsaturated polyester

Advantages




Low viscosity
Fast cure
Low cost
Disadvantages


lower properties than epoxy
large mold shrinkage  sink marks

an incompatible thermoplastic mixed into the resin to form a
dispersed phase in the resin  “low profile” system
Vinyl ester

Resin:



Products of addition polymerization of epoxy resin and
an unsaturated carboxylic acid (vinyl)
unsaturated C=C bonds are at the end of a vinyl ester
molecule  fewer cross-links  more flexible
Cross-linking agent




The polymer is dissolved in styrene
Addition polymerization to form cross-links
Formation of a gigantic molecule
Similar curing reaction as unsaturated polyester resin
Vinyl ester
Vinyl ester
Vinyl ester

Advantages

epoxy-like:



polyester-like:





excellent chemical resistance
high tensile strength
Low viscosity
Fast curing
less expensive
good adhesion to glass fibers due to existence of -OH
Disadvantages:

Large volumetric shrinkage (5 – 10 %)
Vinyl ester
Advantages of thermosetting resins




High strength and modulus.
Less creep and stress relaxation
Good resistance to heat and chemicals
Better wet-out between fibers and matrix due to
low viscosity before cross-linking
Disadvantages of thermosetting resins





Limited storage life
Long time to cure
Low strain to failure
Low impact resistance
Large shrinkage on curing
Thermoplastic matrices

Reading assignment:


Mallick, P.K., Fiber Reinforced Composites . Materials,
Manufacturing and Design, section 2.4 pp 64-69.
Types:


Conventional: no chemical reaction during processing
 Semi-crystalline
 Liquid crystal
 Amorphous
Pseudothermoplastics: molecular weight increase and
expelling volatiles
Thermoplastic matrices

examples:

Conventional
Nylon
 Polyethylene
 Polypropylene
 Polycarbonate
 Polyester
 PMMA

Thermoplastic matrices

examples:

Advanced (e.g.)
Thermoplastic matrices

examples:

Advanced (e.g.)

Polyimide
Thermoplastic matrices
Thermoplastic matrices

Main descriptors:



Linear
Repeatedly meltable
Properties and advantages of thermoplastic
matrices







High failure strain
High impact resistance
Unlimited storage life at room temperature
Short fabrication time
Postformability (thermoforming)
Ease of repair by welding, solvent bonding
Ease of handling (no tackiness)
Thermoplastic matrices
Disadvantages of thermoplastic matrices




High melt or solution viscosity (high MW)
Difficult to mix them with fibers
Relatively low creep resistance
Low heat resistance for conventional
thermoplastics
Metal Matrices

Examples


Al, Ti, Mg, Cu and Super alloys
Reinforcements:
Fibers: boron, carbon, metal wires
 Whiskers
 Particulate

Metal Matrices

Fiber matrix interaction
Fiber and matrix mutually nonreactive and
insoluble
 Fiber and matrix mutually nonreactive but soluble
 Fiber and matrix react to form compounds at
interface

Metal Matrices

Advantage of metal matrix composites
(MMC)

Versus unreinforced metals
higher strength to density ratio
 better properties at elevated temperature
 lower coefficient of thermal expansion
 better wear characteristics
 better creep performance

Metal Matrices

Advantage of MMC

Versus polymeric matrix
better properties at elevated temperature
 higher transverse stiffness and strength
 moisture insensitivity
 higher electrical and thermal conductivity
 better radiation resistance
 less outgassing contamination

Metal Matrices

Disadvantage of MMC

higher cost



high processing temperature
relatively immature technology
complex and expensive fabrication methods with
continuous fiber reinforcements
high specific gravity compared with polymer
 corrosion at fiber matrix interface (high affiliation
to oxygen)
 limited service experience

Ceramic Matrices

Glass ceramics
glass
forming oxides, e.g. Borosilicates and
aluminosilicates
semi-crystalline with lower softening temperature

Conventional ceramics
SiC,
Si3N4, Al2O3, ZrO2
fully crystalline


Cement and concrete
Carbon/carbon
Ceramic Matrices


Increased toughness through deflected crack
propagation on fiber/matrix interface.
Example: Carbon/carbon composites