Carbon fibers (alternatively CF, graphite fiber) are fibers about 5–
10 micrometres in diameter and composed mostly of carbon atoms. Carbon
fibers have several advantages including
high stiffness,
high tensile strength,
low weight,
high chemical resistance,
high temperature tolerance and
low thermal expansion.
These properties have made carbon fiber very popular in aerospace, civil
engineering, military, and motorsports, along with other competition sports.
However, they are relatively expensive when compared with similar fibers,
such as glass fibers or plastic fibers.
A 6 μm diameter carbon filament (running from bottom left to top right)
compared to a human hair
Classification and types
Based on modulus, strength, and final heat treatment temperature, carbon fibers can be
classified into the following categories:
Based on carbon fiber properties, carbon fibers can be grouped into:
, Ultra-high-modulus, type UHM (modulus >450Gpa)
High-modulus, type HM (modulus between 350-450Gpa)
Intermediate-modulus, type IM (modulus between 200-350Gpa)
Low modulus and high-tensile, type HT (modulus < 100Gpa, tensile strength > 3.0Gpa)
Super high-tensile, type SHT (tensile strength > 4.5Gpa)
Based on precursor fiber materials, carbon fibers are classified into:
PAN-based carbon fibers
Pitch-based carbon fibers
Mesophase pitch-based carbon fibers
Isotropic pitch-based carbon fibers
Rayon-based carbon fibers
Gas-phase-grown carbon fibers
Based on final heat treatment temperature, carbon fibers are classified into:
Type-I, high-heat-treatment carbon fibers (HTT), where final heat treatment temperature
should be above 2000°C and can be associated with high-modulus type fiber.
Type-II, intermediate-heat-treatment carbon fibers (IHT), where final heat treatment
temperature should be around or above 1500°C and can be associated with high-strength
type fiber.
Type-III, low-heat-treatment carbon fibers, where final heat treatment temperatures not
greater than 1000°C. These are low modulus and low strength materials.
Properties
Carbon Fiber has High Strength to Weight Ratio (also known as specific strength)
Strength of a material is the force per unit area at failure, divided by its density. Any
material that is strong AND light has a favourable Strength/weight ratio. Materials such as
Aluminium, titanium, magnesium, Carbon and glass fiber, high strength steel alloys all have
good strength to weight ratios.
Carbon Fiber is very Rigid
, Rigidity or stiffness of a material is measured by its Young Modulus and measures how much
a material deflects under stress. Carbon fiber reinforced plastic is over 4 times stiffer than
Glass reinforced plastic, almost 20 times more than pine, 2.5 times greater than aluminium.
Carbon fiber is Corrosion Resistant and Chemically Stable
Although carbon fiber themselves do not deteriorate, Epoxy is sensitive to sunlight and
needs to be protected. Other matrices (whatever the carbon fiber is imbedded in) might
also be reactive.
Carbon fiber is Electrically Conductive
This feature can be useful and be a nuisance. In Boat building It has to be taken into account
just as Aluminium conductivity comes into play. Carbon fiber conductivity can facilitate
Galvanic Corrosion in fittings. Careful installation can reduce this problem.
Fatigue Resistance is good
Resistance to Fatigue in Carbon Fiber Composites is good. However when carbon fiber fails
it usually fails catastrophically without much to announce its imminent break. Damage in
tensile fatigue is seen as reduction in stiffness with larger numbers of stress cycles, (unless
the temperature is hight) Test have shown that failure is unlikely to be a problem when
cyclic stresses coincide with the fiber orientation. Carbon fiber is superior to E glass in
fatigue and static strength as well as stiffness.
Carbon Fiber has good Tensile Strength
Tensile strength or ultimate strength, is the maximum stress that a material can withstand
while being stretched or pulled before necking, or failing. Necking is when the sample cross-
section starts to significantly contract. If you take a strip of plastic bag, it will stretch and at
one point will start getting narrow. This is necking. It is measured in Force per Unit area.
Brittle materials such as carbon fiber does not always fail at the same stress level because of
internal flaws. They fail at small strains.
Testing involves taking a sample with a fixed cross-section area, and then pulling it gradually
increasing the force until the sample changes shape or breaks. Fibers, such as carbon fibers,
being only 2/10,000th of an inch in diameter, are made into composites of appropriate
shapes in order to test.
Fire Resistance/Non Flamable
Depending upon the manufacturing process and the precursor material, carbon fiber can be
quite soft and can be made into or more often integreted into protective clothing for
10 micrometres in diameter and composed mostly of carbon atoms. Carbon
fibers have several advantages including
high stiffness,
high tensile strength,
low weight,
high chemical resistance,
high temperature tolerance and
low thermal expansion.
These properties have made carbon fiber very popular in aerospace, civil
engineering, military, and motorsports, along with other competition sports.
However, they are relatively expensive when compared with similar fibers,
such as glass fibers or plastic fibers.
A 6 μm diameter carbon filament (running from bottom left to top right)
compared to a human hair
Classification and types
Based on modulus, strength, and final heat treatment temperature, carbon fibers can be
classified into the following categories:
Based on carbon fiber properties, carbon fibers can be grouped into:
, Ultra-high-modulus, type UHM (modulus >450Gpa)
High-modulus, type HM (modulus between 350-450Gpa)
Intermediate-modulus, type IM (modulus between 200-350Gpa)
Low modulus and high-tensile, type HT (modulus < 100Gpa, tensile strength > 3.0Gpa)
Super high-tensile, type SHT (tensile strength > 4.5Gpa)
Based on precursor fiber materials, carbon fibers are classified into:
PAN-based carbon fibers
Pitch-based carbon fibers
Mesophase pitch-based carbon fibers
Isotropic pitch-based carbon fibers
Rayon-based carbon fibers
Gas-phase-grown carbon fibers
Based on final heat treatment temperature, carbon fibers are classified into:
Type-I, high-heat-treatment carbon fibers (HTT), where final heat treatment temperature
should be above 2000°C and can be associated with high-modulus type fiber.
Type-II, intermediate-heat-treatment carbon fibers (IHT), where final heat treatment
temperature should be around or above 1500°C and can be associated with high-strength
type fiber.
Type-III, low-heat-treatment carbon fibers, where final heat treatment temperatures not
greater than 1000°C. These are low modulus and low strength materials.
Properties
Carbon Fiber has High Strength to Weight Ratio (also known as specific strength)
Strength of a material is the force per unit area at failure, divided by its density. Any
material that is strong AND light has a favourable Strength/weight ratio. Materials such as
Aluminium, titanium, magnesium, Carbon and glass fiber, high strength steel alloys all have
good strength to weight ratios.
Carbon Fiber is very Rigid
, Rigidity or stiffness of a material is measured by its Young Modulus and measures how much
a material deflects under stress. Carbon fiber reinforced plastic is over 4 times stiffer than
Glass reinforced plastic, almost 20 times more than pine, 2.5 times greater than aluminium.
Carbon fiber is Corrosion Resistant and Chemically Stable
Although carbon fiber themselves do not deteriorate, Epoxy is sensitive to sunlight and
needs to be protected. Other matrices (whatever the carbon fiber is imbedded in) might
also be reactive.
Carbon fiber is Electrically Conductive
This feature can be useful and be a nuisance. In Boat building It has to be taken into account
just as Aluminium conductivity comes into play. Carbon fiber conductivity can facilitate
Galvanic Corrosion in fittings. Careful installation can reduce this problem.
Fatigue Resistance is good
Resistance to Fatigue in Carbon Fiber Composites is good. However when carbon fiber fails
it usually fails catastrophically without much to announce its imminent break. Damage in
tensile fatigue is seen as reduction in stiffness with larger numbers of stress cycles, (unless
the temperature is hight) Test have shown that failure is unlikely to be a problem when
cyclic stresses coincide with the fiber orientation. Carbon fiber is superior to E glass in
fatigue and static strength as well as stiffness.
Carbon Fiber has good Tensile Strength
Tensile strength or ultimate strength, is the maximum stress that a material can withstand
while being stretched or pulled before necking, or failing. Necking is when the sample cross-
section starts to significantly contract. If you take a strip of plastic bag, it will stretch and at
one point will start getting narrow. This is necking. It is measured in Force per Unit area.
Brittle materials such as carbon fiber does not always fail at the same stress level because of
internal flaws. They fail at small strains.
Testing involves taking a sample with a fixed cross-section area, and then pulling it gradually
increasing the force until the sample changes shape or breaks. Fibers, such as carbon fibers,
being only 2/10,000th of an inch in diameter, are made into composites of appropriate
shapes in order to test.
Fire Resistance/Non Flamable
Depending upon the manufacturing process and the precursor material, carbon fiber can be
quite soft and can be made into or more often integreted into protective clothing for
