Carbon fiber
Carbon fiber is favored in manufacturing by engineers and
designers. This is because of the unique properties of carbon fiber. Carbon
fiber is a very strong material and it is also lightweight. It is used in most
manufacturing of machine parts because it is five times stronger than steel and
lighter weight than steel. Carbon fiber is a polymer and is also known as
graphite fiber.
What is carbon fiber?
Carbon fiber is fiber in which carbon atoms are bonded
together to form a long chain of carbon. Carbon fibers are fibers about 5 to 10
micrometers in diameter. Mainly composed of a carbon atom. The carbon fiber has
high stiffness, low weight to strength ratio, high chemical resistance, high
tensile strength, high-temperature tolerance, and low thermal expansion.
How carbon fiber can form?
When carbon atoms are bonded together in crystals that are
more or less aligned parallel to the long axis of the fiber as the crystal
alignment gives the fiber high strength-to volume, then the carbon fiber is
formed.
Carbon fiber is mainly produced from a polymer such as
polyacrylonitrile (PAN), rayon, or petroleum pitch. These polymers are called
precursors.
Synthesis of carbon fiber involves various processes:
Spinning
Carbonization
Graphitization
Spinning:
Polymers such as PAN or rayon are initially spun by chemical
and mechanical processes to enhance the physical properties of the carbon
fiber.
Carbonization:
Carbonization is a process of heating the polymer filament
to drive off the non-carbon atom and form the final carbon fiber.
Heating:
The spun PAN filaments are then heated to 300C in the air to
break many of the hydrogen bonds and oxidize the material.
Graphitization:
The oxidized PAN is then placed into the furnace which has
an inert atmosphere of a gas such as argon and heated to approximately 2000C to
change the molecular bond structure, which is called graphitization.
When all the conditions of heating are fulfilled, then these
chains bond side to side (ladder polymers), forming narrow graphene sheets
which finally merge as a single columnar filament called carbon fiber sheet.
Describe the structure of carbon fiber?
Carbon fiber consists of carbon atoms arranged in a regular
hexagonal pattern as in graphite structure, the only difference is how sheets
interlock.
Depend upon the precursor to make the fiber:
Depending upon the precursor to make the fiber, carbon fiber
may be
·
Turbostratic
·
Graphitic
Turbostratic:
In Turbostratic carbon fiber, the sheets of carbon atoms are
haphazardly folded and crumpled together. Turbostratic have a hybrid structure
with both graphitic and Turbostratic parts present. Carbon fibers derived from
polyacrylonitrile (PAN) are Turbostratic. Turbostratic have high ultimate
tensile strength.
Graphite:
The atomic structure is almost similar to that of graphite.
Graphite is a crystalline material in which the sheets are stacked parallel to
one another in a regular fashion. The carbon fiber derived from mesophase pitch
is graphite after heat treatment at a temperature exceeding 2200. The
intermolecular forces between the sheets are relatively weak Van der Waals
forces, responsible for the softness and brittle characteristics of graphite.
Graphite has a high Young’s modulus, high stiffness, resistance to extension
under load, and high thermal conductivity.
What is composite carbon fiber?
Carbon composite is
extremely strong and light fiber-reinforced plastic that contains carbon
fibers. Composite carbon fiber has a high strength-to-weight ratio and
stiffness. Because of its properties of it is expensive to produce and has many
applications in manufacturing such as aerospace, automotive, civil engineering,
etc.
What are carbon sheets?
There are a variety of carbon sheets depending upon their
applications in various manufacturing fields. These plates have a specific
thickness and multiple laminations of carbon in an epoxy matrix. Few types of
carbon sheets most commonly used are
·
Quasi-isotropic carbon fiber sheet
·
Shock-resistant carbon fiber sheet
·
Prepreg carbon fiber sheet
·
UV resistance bridge strengthening carbon fiber
sheet
·
Soft carbon fiber sheet with good flexibility
long durability high elasticity
·
Lightweight carbon sheet with bending shearing
reinforcement for concrete beams
·
Strong rigidity carbon sheet with high elastic
modulus durable
·
Low-density thin carbon fiber sheet
·
Professional carbon fiber fabric sheets Eco-friendly
Excellent dimensional stability
·
Flexible carbon fiber concrete substrate applied
anti-acid easily cut
·
Carbon fiber laminate sheet
What are the types of carbon fiber?
Depending upon the properties, precursor and
heat temperature carbon fiber are classified as:
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 are not greater than
1000°C. These are low modulus and low strength materials.
Describe the properties of carbon fiber?
The preferences of carbon fiber over material because of its
properties. Some important properties of carbon fiber are
Stiffness
brittleness
Rigidity
Non- Flammable
High strength to weight ratio
Corrosion-resistant and chemically stable
Electrically conductive
Fatigue Resistance
Relatively expensive
Low coefficient of thermal expansion
Thermal conductivity of carbon fiber
Non- poisonous, Biologically inert, X-ray permeable
Stiffness:
Carbon fiber is extremely strong. The stiffness of a material
is measured by the modulus of elasticity. The modulus of carbon fiber is
typically 33msi (228 Gap) and its ultimate tensile strength is 500 ksi ( 3.5Gpa
).
Brittleness:
Carbon fiber is very strong, made up of strong covalent bonds,
and brittle. When the fiber sheet is allowed to bend, the fiber brittle at even
very low strain.
Rigidity:
Rigidity is the capability of a material to deflect or
endure under stress. It is measured by the Young Modulus or modulus of
elasticity. The modulus of carbon fiber is typically 33msi (228 Gap) and its
ultimate tensile strength is 500 ksi (3.5Gpa).
Non- flammable:
Due to the atomic and macrostructure of carbon fiber, the
carbon fiber is non-flame material. This property of carbon fiber is useful to
many industries for the manufacturing of materials in the modern world.
High strength to weight ratio:
The strength of a material is the ability of a material to
withstand force. Any strong material has a good strength to weight ratio.
Carbon fiber is a strong material and has a good strength-to-weight ratio.
Corrosion resistance and chemical stability:
Carbon fiber itself is chemically stable and resistant to
corrosion. If carbon fiber is embedded in another material, then it might be
reactive.
Electrically conductive:
Carbon fiber has a high conductivity of about 8.33c. The
thermal conductivity of carbon fiber has proven, it is the best material for
aircraft and boats. It is also used for the
transformation of electricity with less resource consumption.
Fatigue resistance:
Carbon fiber has a good fatigue resistance. Carbon fiber is
superior to glass in fatigue.
Relative expensive:
Because of its extensive strength capability over the
weight, it has higher demand in the market. The customers are willing to pay
more for it because of its unique properties.
Low coefficient of thermal expansion:
Material can expand
or contract when the applied temperature goes up and down. Carbon has a low
coefficient of thermal expansion. Low coefficient thermal expansion carbon
fiber is very suitable for applications where small movements of machinery are
concerned. For example, it has many applications in optical machinery such as
in telescopes.
Thermal conductivity of carbon fiber:
Thermal conductivity is the quantity of heat transmitted
through a unit thickness, in a direction normal to the surface of the material.
The carbon fiber has many variations of the theme. The specific carbon fiber has
higher thermal conductivity than graphite carbon fiber. For better features,
carbon fiber has been designed for high or low thermal conductivity.
Non-poisonous, biologically inert, X-ray permeable:
Carbon fiber is
non-poisonous, biologically inert, and x-ray permeable. These characters make
carbon fiber special in Medical applications. X-ray surgical instruments are
used in development in prosthesis use, tender repair. Carbon fiber is
non-poisonous but can be irritated, so long-term use of this needs to be
limited.
What are the applications of carbon fiber?
Applications of carbon fiber:
Because of the unique properties of carbon fiber, it has
many applications in almost every manufacturing process of machinery and
engineering. Some main applications of carbon fiber are
·
Composite material
·
Electromagnetic properties
·
Textiles
·
Biological inertness and x-ray permeability
·
Microelectrodes
·
Flexible heating
·
Electrical conductivity
Composite material:
Composite material is used in high-temperature
applications. Composite material finds its use infiltration of high-temperature
gases, as an electrode with high surface area, impeccable corrosion resistance,
and as an anti-static component. It is also used in aerospace applications
displacing other metals such as aluminum, transportation infrastructure
especially for airport pavement
Electrical
properties:
Carbon fiber
is used in large generator retaining rings, radiological equipment.
Biological
inertness and x-ray permeability:
Carbon fiber is non-poisonous, biologically inert, and x-ray
permeable. These characters make carbon fiber special in Medical applications.
X-ray surgical instruments are used in development in prosthesis use, tender
repair. Carbon fiber is non-poisonous but can be irritated, so long-term use of
this needs to be limited.
Textiles:
Carbon fiber filament yarns are
used in several processing techniques, the direct uses for prepregging,
filament winding, pultrusion, weaving, braiding, etc.
Microelectrodes:
Carbon fibers are used for the fabrication
of carbon-fiber microelectrodes. Carbon-fiber microelectrodes are used either
in amperometry or fast-scan cyclic voltammetry for the detection of biochemical
signaling.
Flexible heating:
Due to its chemical inertness, it
can be used relatively safely amongst most fabrics and materials. Many applications
can be seen in DIY heated articles of clothing and blankets.
Electrical conductivity:
Carbon fiber has many electrical
applications in automobile hoods, novel tooling, casing and bases for
electronic equipment, EMI and RF shielding, and brushes.
Conclusion:
Carbon fiber is unique in its
properties and is used in vast fields of life. This field is extending with
many developments, which has applications mechanical and electrical properties
that may be useful in making new fibers, submicroscopic test tubes, and new
semiconductor material. The latest development in carbon fiber technology is
tiny carbon tubes called nanotubes.
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