Transcript Slide 1

INTRODUCTION TO ADVANCED
COMPOSITE MATERIALS
Dr. ZAFFAR M. KHAN
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Fabrication
Introduction
Processing/NDT
INDUSTRIAL
COMPOSITES
Design Analysis
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Industrial Application
Scope
Historical background, nature and advantages of composites
Types of matrices
Fibers and their characterization
Physical and mechanical properties of composites
Application in aircraft, sports goods, medical, civil engineering and automobile
industries
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First Composite Solo Flight
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Relative importance of Engineering Materials
with respect to time period
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Trends of Carbon Fiber Composite Growth
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Carbon Composites for Defence Systems
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Composite Materials
Composite materials are
macroscopic combination of
two or more materials each
having distinct properties. It is
composed of:
1.
2.
3.
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Matrix (Black)
Reinforcement (White)
Iinterphase
Advantages of Composite Materials
Significant weight saving which increases
payload and/or range along with fuel
saving.
Maximum specific strength and stiffness
make them lighter than aluminum,
stronger than steel.
Permits aero-elastic tailoring of structural
components.
Flexibility of Design
Integrated structures diminishes
application of rivets.
Enhanced fatigue life.
Absence of corrosion.
Reduced operational, manufacturing
and maintenance cost.
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Comparison of Composites with Metals
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Aero-elastic Composite Structure
The composite structure is tailored to
meet varying aerodynamic
requirements in aircrafts, cars wind
and rotor blades. It reduces drag and
enhances energy conservation.
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Flexibility of Composite Design
Influence of Vibrations on Composites
The vibration damping characteristics
of composites are far superior as
Compared to metals for following
reasons;
1. Matrix visco-elastic effects and
micro-cracking
2. Blunting of crack by in fibers
transverse direction
3. Debonding and sliding of fibers
in axial direction.
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Integrated Structure
Integrated composite structure
reduces rivets and associated weight
which leads to integrated structure of
aircraft, automobiles and other
engineering systems.
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Matrix Constituent
Roles:
Binds and holds reinforcemaent
together
Determines composite shape and
geometry
Transfers stresses to reinforcement
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Types:
Ceramic (Temp < 6000°F)
Metallic (Temp < 4000°F)
Polymeric (Temp < 600°F)
Determine:
Environmental resistance
Shelf Life
Compressive & transverse
mechanical properties of composite
Ceramic Matrix
Oxides, carbides, nitrides, borides and silicates characterizes high degree
of thermal and dimensional stability.
Manufacturing Process:
Cast from slurries or processed into shape with organic binder and then fired/
sintered/ cured at very high temperature.
Examples:
Silicon carbide filament in Silicate matrix
Boron carbide in Alumina matrix
Aluminum oxide in Alumina matrix
Metal particles in ceramic matrix  CERMETS
Applications:
Rocket nose cone and Nozzle
Combustion Chamber
Skin of space plane/ spacecraft
Problem Areas:
Interface problem
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Metal Matrix
Relatively lower densities of aluminum, titanium and magnesium are reinforced
by high strength/ stiffness fibers. Organic fibers are not used due to high
processing temperatures. Most common fibers are;
Metal fibers of beryllium, molybdenum, steel and tungsten
Boron, silicon carbide, silicon boride coated fine wires
Whiskers of aluminum oxide, boron carbide or silicon carbide
Manufacturing Process:
Metal matrix may be coated onto fibers by electro deposition, vapor
deposition or plasma spray followed by hot pressing
Fibers can be infiltrated with liquid metal under high process
Fiber pressed between metal foils and sintered with powder metals
Examples:
Aluminum, titanium alloys, silver, magnesium, cobalt and copper matrices
Applications:
Space shuttle, piston ring, connecting rods, suspension components
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Polymeric Matrix
Composed of long chains of hydro carbons
Thermoplastics:
Softens when heated and hardens
when cooled.
Can be recycled.
Relatively tough
Low dimensional stability.
Styrenes, Vinyls, Acrylics,
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Thermosets:
Hardens when heated.
Composed of long molecular cross
links.
Cannot be recycled.
Relatively brittle.
Relatively greater dimensional
tolerance.
Epoxies, urathanes, phenolics.
Comparison of Thermoset Versus Thermoplastic
PROPERTY
Melt Viscosity
Fiber Impregnation
Prepreg Tack
Prepreg Drape
Prepreg Stability at 0° F
Processing Cycle
Processing Temperature
Mechanical Properties
Environmental Durability
Damage Tolerance
Database
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THERMOSET
THERMOPLASTIC
(FIBERITE 931 EPOXY) (ICI APC-2 PEEK)
Low
High
Easy
Difficult
Good
None
Good
Poor
6 mos. -1 yr.
Indefinite
1-6 Hrs
15 sec 6 hr
350° F
700° F
Good
Good
Good
Exceptional
Average
Good
Large
Average
Structural Performance Ranking of Materials
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Temperature Response of Ceramic, Metallic &
Polymeric Composites
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Polymeric composites have maximum specific strength but has poor strength
at elevated temperatures. Metal and ceramic composites retain their lower
mechanical properties at elevated temperature. Selection of composites is
determined by environmental temperatures.
Properties of Polymeric Matrices
EPOXY (THERMOSET)
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Most widely used matrix in hi-tech applications
Outstanding adhesion
Low shrinkage during cure
Easy to process forgiving
Strong, tough
Extensive, reliable data base
POLYESTER (THERMOSET)
 Most widely used matrix for less demanding applications
 High shrinkage during cure
 Poorer adhesion than epoxy
 Very easy to process ; lower pressures and temperatures and shorter cure cycles than epoxy.
 Lower cost than epoxy
 In general, poorer properties than epoxy (and less expensive)
POLYIMIDE (THERMOSET)
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Primarily for service at high temperature i.e. 600 F
Higher cost than epoxy
More difficult to process than epoxy ; more complex cure cycles, requires higher temperatures are pressures
Dark colours only
High brittleness
Propreg does not drape well ( tends to be a little shiff)
BISMALEIMIDE (THERMOSET)
 Proposed to fill the gap between polyimide and high temperature epoxies i.e. 450 – 500 degrees F
 Better strength than epoxy at high temperature
 It has relatively simple are cycles more like epoxy than polyimide (Thus it is relatively easy to process
 Application in X-wing vertical take off/landing sibors by Aircraft /copter.
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PHENOLIC (THERMOSET)
Expensive and difficult to process; requires high cure pressure
Good electrical resistance
• Self extinguishing and not toxic, thus it has received interest for aircraft interiors (for example :
graphite fabric reinforced phenolic facings for honeycomb floor panels )
URETHANE (THERMOPLASTIC)
Good toughness and abrasion resistance
Easily foamed and low heat transfer (thus, a common use is insulation )
Limited in service temperature
Commonly used in Reuction Injection Molding (RIM) to produce strong, stiff, light weight
“Self-skinned” structures
Reinforced with carbon fiber Ejection seats
PEEK (THERMOPLASTIC)
Tough, high impact resistance, high fracture toughness
Excellent abrasion resistance
Excellent solvent resistance
Low moisture absorption
Very high cost
New, not much data available
Requires very high processing temperature (600 degrees F) which complicates manufacturing
Prepregs are stiff (no drape); thus, flat laminates must first be made, then laminates
must be formed to shape with high temp and pressure. Manufacturing with prepregs
is still in development stage.
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Thermoset Composites
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Thermoplastic Composites
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Thermoplastic Composites
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Evolution of Epoxy Resin
Poly functional epoxy resin contains more than two epoxide group
FIRST GENERATION EPOXIES:
Example: NARMCO 5208, CIBA GEIGY – 914
Better dimensional stabile but inherently brittle.
Composed of:
 Tetra Glycidyl Derivative (Wt Fraction : 38.2 %)
 Triglycidyl Ether (33.4%)
 Dicyandiamide (5.0%)
 Poly Ether Sul Phone (23.4)
SECOND GENERATION EPOXIES:
Example: NARMCO 5245, CIBA GEIGY-924
 Addition of CTBN to original formulation
 Better damage tolerance, reduced hot /wet
performance.
 Lead to phase separation which imparts desired
toughness.
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Reinforcement Constituent
1.
2.
3.
4.
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Particulate: Good compression
strength but poor tensile properties,
and particles in cement.
Flakes:
Effective solvent
resistant but difficult fabrication.
Whiskers: High degree of
strength but poor crack stopping
properties.
Fibers:
Better structural
properties, crack stopping
properties, flexibility of design
requirement by changing
orientation of fibers 0°, +45°, 90°
Stacking sequence
Types of fibers i.e. glass, carbon,
kevlar & carbon
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Milled Carbon Fibers
Carbon Fiber Pellets
Chopped Carbon Fibers
Carbon Fiber Mat
Micrographs of Carbon, Kevlar and Glass Fibers
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Properties of High Performance Synthetic Fibers
CARBON
(2-Dimension)
GLASS
(3 Dimension)
ADVANTAGES
Max specific strength
Max specific modulus
High temp resistance
Tough
Light weight
No galvanic corrosion
High temp resistance
No galvanic corrosion
Low notch sensitivity
DISADVANTAGES
Expensive
Low impact resistance
Promotes oxidation
Difficult machining
Poor compression
Absorbs moisture
Difficult machining
Poor coupling to resin
High density
Low stiffness
APPLICATIONS
Rocket motors
Aircrafts members
Leading edges, ropes
Ballistic protection
COST INDEX
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KEVLAR
(1 Dimension)
High (6-7)
Intermediate (3)
Water tank, bathroom
accessories, shelters
Low (1-2)
Microstructure of Carbon Fibers
The covalently bonded aromatic
chains of carbon fiber in the axial
direction are held together by weak
Wander wall bonds in transverse
direction. The alignment of chains in
axial direction determines their
outstanding strength.
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Fabrication of Carbon Fiber
Carbonization:
200-250°F
Oxidation:
1000°C 
Graphitization:
2500-3000°C 
Etching of fiber surface
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Processing Temperature
The higher degree of temperature and
tension during graphitization process
leads to greater alignment of carbon
chains and superior mechanical
properties of carbon fibers, T-300
(Boeing-727, 737, 747 and Airbus310) and T-800 (Boeing-777, Airbus380, Osprey V22 and JSF).
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Variation of Mechanical Properties of Carbon Fiber
With Respect to Temperature
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Chemical Kinetics of during Curing of CFRP
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Kevlar Fibers
Kevlar: Aromatic carbon chains are held together by amide group (-CH-NH-).
Concentrated solution in strong mineral acid is processed through spinnerets into
neutralizing bath. The fibers are washed, dried and heated in nitrogen at high
temperature under tension.
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Properties of Kevlar Fibers
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Glass Fibers
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Weave Architecture
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Through Thickness Stitching
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Fiber Architecture
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Prepreg
Prepreg: The resin is impregnated in
fibers by passing fibers through resin
bath, oven and driers. The resin is
advanced from A to B stage. The
ready to mold material is stored for
application.
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Unidirectional and Fabric Prepreg
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Composite Materials Summary
Composite Materials
Matrix
Ceramic
Metalic
Interphase
Polymers
Particulate
Thermoset
Phenolics
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Polyester
Reinforcment
Flakes
Thermoplastic
Epoxy
Acrylics
PEEK
Fibers
Carbon
Carbonates
Kevlar
Glass
THANK YOU
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