High Performance Fibers and
Fibrous materials
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:
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:
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
?* = 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
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:
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
The probability for the fiber to survive
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
Materials for fiber reinforced composites
? Statistical treatment of fiber
strength
? Weibull distribution of fiber strength
? Weibull’s assumption:
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
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
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
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:
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:
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
?* = 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
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:
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
The probability for the fiber to survive
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
Materials for fiber reinforced composites
? Statistical treatment of fiber
strength
? Weibull distribution of fiber strength
? Weibull’s assumption:
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
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
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
