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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?
� Two or more phases with different properties
• Why composite materials?
� 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
2
4
6
8 Specific gravity
(g/cc)
Steel
Al alloy
Ti alloy
Carbon/epoxy
Kevlar/epoxy
materials
Comparison of specific gravities
0
200
400
600
800
1000
1200
1400
Tensile strength (MPa)
Steel
Al alloy
Ti alloy
Carbon/epoxy
Kevlar/epoxy
Materials
Comparison of tensile strength
0
4
8
12
16Modulus to weight
ratio (109m)
Steel
Al alloy
Ti alloy
Carbon/epoxy
Kevlar/epoxy
Materials
Comparison of modulus to
weight ratio
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
� However, for a given tensile sample, tensile stiffness
has nothing to do with length or L = 1 may be
assumed
1 when ===
==
LA
W
AL
W
ALVW
ρ
ρρ
( )
ερ
ερ
ερεεσ
W
FE
W
F
W
F
A
FE
=∴
====Q
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:
� Textbook Chapter 2 Fibers and matrices
� Fibers
� 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
f i b e r s T e n s i l e
s t r e n g t h
( M P a )
T e n s i l e
M o d u l u s
( G P a )
C o e f f . O f
T h e r m a l
E x p e n s i o n1 0 - 6 / K
D ie le c t r i c
C o n s t . ( a )
E - g l a s s 3 4 5 0 7 2 . 5 5 . 0 6 . 3
S - g l a s s 4 5 9 0 8 6 . 0 5 . 6 5 . 1
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
22
*16
=L
dEb
πσ
2L
EIcP =
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
� e.g. Carbon, glass, SiC
� Some ductile
� 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:
κπ
κ64
4dEEIM ==
E = Young’s Modulus
d = fiber diameter
κ = curvature
Materials for fiber reinforced composites
� The strength of reinforcements
� Fiber failure in bending
�Stress on surface
� Tensile stress:
2
dEκσ =
E = Young’s Modulus
d = fiber diameter
κ = curvature
Materials for fiber reinforced composites
� The strength of reinforcements
� Fiber failure in bending
�Stress on surface
� Maximum curvature
Ed
*max
2σκ =
σ* = 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
NLLLLL ∆++∆+∆+∆= L321
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:
variationoft Coefficien
oflength a fiber with ofStrength
oflength a fiber with ofStrength
)1(2.41/ 5/1
=
=
=
−−= −
CV
l
nl
CVn
l
nl
lnl
σ
σ
σσ
Materials for fiber reinforced composites
� Statistical treatment of fiber strength
� Weakest Link Theory (WLT)
�define nσ = No. of flaws per unit length causing
failure under stress σ. �For the first element, the probability of failure
11 LnPf ∆= σ
The probability for the fiber to survive
)1()1)(1( 21 fNffs PPPP −−−= L
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
)](exp[ 21 fNffs PPPP +++−= L
)exp()](exp[21 σσσσ LnLnLnLn
N−=∆++∆+∆−= L
Materials for fiber reinforced composites
� Statistical treatment of fiber strength
� Weibull distribution of fiber strength
�Weibull’s assumption:
m
nL
=
0
0
σσ
σ
m = Weibull shape parameter (modulus).
σ0 = 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
−−=
m
fL
LP
00
exp1σσ
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 σ <σ0, the probability of failure is small if m is large.
� When σ ≥σ0, 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
m
sL
LP
−=
00
)ln(σσ
m
s L
L
P
=
00
1ln
σσ
( ) ( ) ( ) ( )00 lnlnlnln1
lnln σσ mmLLPs
−+−=
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 Polymer-
Fiber 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
Properties minimum desired Typicalepoxy
Tensile strength
(MPa)
70 >100 ---
Modulus (GPa) 2.0 >3.0 3.8
Ultimate Strain(%)
5 >10 1 - 2
Glass transition
temperature (°C)121 >177 121
Polymer
Target net resin properties
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
� 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
� Resin microstructure:
� 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: self-
polymerization →
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:
� excellent chemical resistance
� high tensile strength
� polyester-like: � 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