High Performance Fibers and
Fibrous materials
Yiping Qiu
Donghua University
Outline
? Carbon fibers
? Glass fibers
? Aramid fibers
? Ultra High Modulus Polyethylene fibers
? Carbon nanotubes
? Ceramic fibers
? Mechanical properties of fibers
Carbon fibers
? Reading assignment
? Hull and Clyne,Chapter 2 Fibres and
Matrices,An Introduction to Composite
Materials,2nd ed,Cambridge University
Press,Pages 9 –30.
Carbon fibers
? Manufacturing processes
? Structure and properties
Carbon fibers
– Manufacturing processes
? Thermal decomposition of fibrous organic
precursors
? Extrusion of pitch
Carbon fiber manufacturing processes
– 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%)
Carbon fiber manufacturing processes
– PAN (polyarylonitrile) based carbon fibers
? PAN fibers
?Stabilization at 200-300° C in O2,depolymerization &
aromatization,converting thermoplastic PAN to a nonplastic
cyclic or ladder compound
?Carbonization at 1000-1500° C in an inert atmosphere to get
rid of noncarbon elements
?Stretch and graphitization at >1800° C,formation of
turbostratic structure
Stabilization of PAN fibers
Pitch based carbon fibers
? pitch - high molecular weight byproduct of distillation
of petroleum
– heated >350° C,condensation reaction,formation of
mesophase (Liquid crystal),Structure of mesophase pitch
?melt spinning into pitch fibers
?Oxidation at a temperature below softening temperature
?conversion into graphite fibers at ~2000° C without tension
Pitch based carbon fibers
– Advantages
? Much higher degree of graphitization than
polymer based carbon fibers
? High strength and modulus
? High thermal conductivity,even much better
than copper
Structure of carbon fibers
? Turbostratic structure
? Fiber structure
Carbon fibers
– Advantages of all carbon fibers
? High tensile strength and tensile modulus
? Nonreactive
– Resistance to corrosion
– High heat resistance
– high tensile strength at elevated temperature
? Low density
Carbon fibers
– Disadvantages
? High cost
? Brittle
? Oxidation at > 400oC
Carbon fibers
? Other interesting properties
– Lubricating properties
– Electrical conductivity
– Thermal conductivity
– Low to negative thermal expansion
coefficient
Difference between carbon fiber and
graphite fiber
? 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)
Glass fibers
– Compositions and properties
– Advantages and disadvantages
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
Glass fibers
? Types and Properties
– E-glass (for electric)
? draws well
? good strength & stiffness
? good electrical and weathering properties
Glass fibers
? Types and Properties
– C-glass (for corrosion)
? good resistance to corrosion
? low strength
Glass fibers
? Types and Properties
– S-glass (for strength)
? high strength & modulus
? high temperature resistance
? more expensive than E
Glass fibers
– Production
? Melt spinning
Glass fibers
? sizing:
– purposes
? protest surface
? bind 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
Glass fibers
? Advantages
– high strength
– same strength and modulus in transverse
direction as in longitudinal direction
– low cost
Glass fibers
? Disadvantages
– relatively low modulus
– high specific density (2.6 g/cc)
– moisture sensitive
PPTA fibers
? Structure
– Poly(p-phenylene terephthalamide) (PPTA)
– Polyamide with benzene rings between amide
groups
– Liquid crystalline
– Planar array and pleated system
PPTA fibers
? Types
– Kevlar 29,E = 50 GPa
– Kevlar 49,E = 125 GPa
– Kevlar 149,E = 185 GPa
– Kevlar 129 etc
– Twaron 1000
– Twaron 2000
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
Grade distribution for test 2
0
5
10
15
20
25
30
9 29 49 69 89 110
Test 2
Test 1
Test 2
Test 1
Materials for fiber reinforced composites
? Spectra fibers
– 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
Carbon Nanotube
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 relatively 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:
???
64
4d
EEIM ??
E= Young’s Modulus
d = fiber diameter
? = curvature
Materials for fiber reinforced composites
? The strength of reinforcements
– Fiber failure in bending
?Stress on surface
– Tensile stress:
2
dE?? ?
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
Ed
*
m a x
2 ?? ?
?* = 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 ????????? ?321
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:
v ar i a t i o nof C ef f i c i e n t
ofl e n g t h a f i b e r w i t h ofS t r e n g t h
ofl e n g t h a f i b e r w i t h ofS t r e n g t h
)1(2.41/
5/1
?
?
?
???
?
CV
l
nl
CVn
l
nl
lnl
?
?
??
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
11 LnP f ?? ?
The probability for the fiber to survive
)1()1)(1( 21 fNffs PPPP ???? ?
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
)](ex p [ 21 fNffs PPPP ????? ?
)e x p ()](e x p [ 21 ???? LnLnLnLn N ?????????? ?
Materials for fiber reinforced composites
? Statistical treatment of fiber strength
– Weibull distribution of fiber strength
?Weibull’s assumption:
m
nL ??
?
?
???
?
?
0
0 ?
?
?
m = Weibull shape parameter (modulus)
?0 = Weibull scale parameter,characteristic
strength.
Materials for fiber reinforced composites
? Statistical treatment of fiber strength
– Weibull distribution of fiber strength
?Thus
?
?
?
?
?
?
?
?
???
?
???
?
???
?
???
???? m
f L
LP
00
e xp1 ??
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
m
s L
LP
???
?
???
?
???
?
???
???
00
)l n ( ??
m
s L
L
P ???
?
???
?
???
?
???
??
???
?
???
?
00
1ln
?
?
? ? ? ? ? ? ? ?00 lnlnlnln1lnln ?? mmLLP
s
?????
?
?
?
?
?
???
?
???
?
Mesophase pitch
Turbostratic structure
Structure of carbon fiber
A,Skin region
B,Core region
C,Hairpin defect
D,Wedge
disclination
Structure of carbon fiber
Reference Book
Fiber properties
Glass fiber properties
PPTA fiber structure
Glass fiber structure
Fiber molecular structures
Fibrous materials
Yiping Qiu
Donghua University
Outline
? Carbon fibers
? Glass fibers
? Aramid fibers
? Ultra High Modulus Polyethylene fibers
? Carbon nanotubes
? Ceramic fibers
? Mechanical properties of fibers
Carbon fibers
? Reading assignment
? Hull and Clyne,Chapter 2 Fibres and
Matrices,An Introduction to Composite
Materials,2nd ed,Cambridge University
Press,Pages 9 –30.
Carbon fibers
? Manufacturing processes
? Structure and properties
Carbon fibers
– Manufacturing processes
? Thermal decomposition of fibrous organic
precursors
? Extrusion of pitch
Carbon fiber manufacturing processes
– 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%)
Carbon fiber manufacturing processes
– PAN (polyarylonitrile) based carbon fibers
? PAN fibers
?Stabilization at 200-300° C in O2,depolymerization &
aromatization,converting thermoplastic PAN to a nonplastic
cyclic or ladder compound
?Carbonization at 1000-1500° C in an inert atmosphere to get
rid of noncarbon elements
?Stretch and graphitization at >1800° C,formation of
turbostratic structure
Stabilization of PAN fibers
Pitch based carbon fibers
? pitch - high molecular weight byproduct of distillation
of petroleum
– heated >350° C,condensation reaction,formation of
mesophase (Liquid crystal),Structure of mesophase pitch
?melt spinning into pitch fibers
?Oxidation at a temperature below softening temperature
?conversion into graphite fibers at ~2000° C without tension
Pitch based carbon fibers
– Advantages
? Much higher degree of graphitization than
polymer based carbon fibers
? High strength and modulus
? High thermal conductivity,even much better
than copper
Structure of carbon fibers
? Turbostratic structure
? Fiber structure
Carbon fibers
– Advantages of all carbon fibers
? High tensile strength and tensile modulus
? Nonreactive
– Resistance to corrosion
– High heat resistance
– high tensile strength at elevated temperature
? Low density
Carbon fibers
– Disadvantages
? High cost
? Brittle
? Oxidation at > 400oC
Carbon fibers
? Other interesting properties
– Lubricating properties
– Electrical conductivity
– Thermal conductivity
– Low to negative thermal expansion
coefficient
Difference between carbon fiber and
graphite fiber
? 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)
Glass fibers
– Compositions and properties
– Advantages and disadvantages
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
Glass fibers
? Types and Properties
– E-glass (for electric)
? draws well
? good strength & stiffness
? good electrical and weathering properties
Glass fibers
? Types and Properties
– C-glass (for corrosion)
? good resistance to corrosion
? low strength
Glass fibers
? Types and Properties
– S-glass (for strength)
? high strength & modulus
? high temperature resistance
? more expensive than E
Glass fibers
– Production
? Melt spinning
Glass fibers
? sizing:
– purposes
? protest surface
? bind 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
Glass fibers
? Advantages
– high strength
– same strength and modulus in transverse
direction as in longitudinal direction
– low cost
Glass fibers
? Disadvantages
– relatively low modulus
– high specific density (2.6 g/cc)
– moisture sensitive
PPTA fibers
? Structure
– Poly(p-phenylene terephthalamide) (PPTA)
– Polyamide with benzene rings between amide
groups
– Liquid crystalline
– Planar array and pleated system
PPTA fibers
? Types
– Kevlar 29,E = 50 GPa
– Kevlar 49,E = 125 GPa
– Kevlar 149,E = 185 GPa
– Kevlar 129 etc
– Twaron 1000
– Twaron 2000
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
Grade distribution for test 2
0
5
10
15
20
25
30
9 29 49 69 89 110
Test 2
Test 1
Test 2
Test 1
Materials for fiber reinforced composites
? Spectra fibers
– 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
Carbon Nanotube
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 relatively 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:
???
64
4d
EEIM ??
E= Young’s Modulus
d = fiber diameter
? = curvature
Materials for fiber reinforced composites
? The strength of reinforcements
– Fiber failure in bending
?Stress on surface
– Tensile stress:
2
dE?? ?
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
Ed
*
m a x
2 ?? ?
?* = 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 ????????? ?321
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:
v ar i a t i o nof C ef f i c i e n t
ofl e n g t h a f i b e r w i t h ofS t r e n g t h
ofl e n g t h a f i b e r w i t h ofS t r e n g t h
)1(2.41/
5/1
?
?
?
???
?
CV
l
nl
CVn
l
nl
lnl
?
?
??
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
11 LnP f ?? ?
The probability for the fiber to survive
)1()1)(1( 21 fNffs PPPP ???? ?
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
)](ex p [ 21 fNffs PPPP ????? ?
)e x p ()](e x p [ 21 ???? LnLnLnLn N ?????????? ?
Materials for fiber reinforced composites
? Statistical treatment of fiber strength
– Weibull distribution of fiber strength
?Weibull’s assumption:
m
nL ??
?
?
???
?
?
0
0 ?
?
?
m = Weibull shape parameter (modulus)
?0 = Weibull scale parameter,characteristic
strength.
Materials for fiber reinforced composites
? Statistical treatment of fiber strength
– Weibull distribution of fiber strength
?Thus
?
?
?
?
?
?
?
?
???
?
???
?
???
?
???
???? m
f L
LP
00
e xp1 ??
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
m
s L
LP
???
?
???
?
???
?
???
???
00
)l n ( ??
m
s L
L
P ???
?
???
?
???
?
???
??
???
?
???
?
00
1ln
?
?
? ? ? ? ? ? ? ?00 lnlnlnln1lnln ?? mmLLP
s
?????
?
?
?
?
?
???
?
???
?
Mesophase pitch
Turbostratic structure
Structure of carbon fiber
A,Skin region
B,Core region
C,Hairpin defect
D,Wedge
disclination
Structure of carbon fiber
Reference Book
Fiber properties
Glass fiber properties
PPTA fiber structure
Glass fiber structure
Fiber molecular structures
