ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
I
Vol-03, Issue-04, April 2015
A REVIEW ON CARBON FIBERS
B. Sandhya rani1, Dr.A.Ramesh2, B.Durga Prasad3, C.Mohannaidu3
1Assoc.Prof,
Department of Mechanical Engineering, GATES Institute of Technology, Gooty,
AP, India. [email protected]
2Principal GATES Institute of Technology, Gooty, Anantapur, A.P, India
3Profesor, Dept. of Mechanical Engineering, JNTUA, Anantapur, AP, India
4Asst.Prof, Dept.of Mechanical Engg., GATES Institute of Technology, Gooty, AP, India
[email protected]
ABSTRACT
Carbon fiber/carbon matrix (C-C) composites are being considered for high-temperature
structural applications. The most important of these applications require the C-C components to
operate in oxidizing environments. Concepts currently being pursued to provide oxidation
protection for structural C-C composites are based on earlier work conducted with graphite and
the successfully employed oxidation-protected C-C material developed for the shuttle orbiter
vehicles. Present C-C applications can be classified either as limited-life or extended-life
depending on the component duty cycle. Limited-life applications generally require minutes to
hours of operation at temperatures greater than 1650°C with minimal thermal cycling. The
principal concerns for limited-life oxidation protection are coating erosion, coating spallation,
and the oxygen permeability of intact coatings. Dense coatings of Si3N4 or SiC have been shown
to perform well at temperatures in the 1700° to 1800°C range. Extended-life applications involve
numerous thermal cycles at temperatures below 1650°C and hundreds of hours of operation. Here
C-C materials modified with boron and coated with dense Si3N4 or SiC outer coatings and boronrich inner layers are currently the topic of extensive development.
Keywords: CF, composites, reinforcing material, Glass, Armand.
1. INTRODUCTION
Carbon Fibers are a new breed of high-strength materials. Carbon fiber has been described
as a fiber containing at least 90% carbon obtained by the controlled pyrolysis of appropriate fibers.
Carbon fibers have found wide application as constituents of composite materials such as
reinforced polymers and metals. Carbon fibers provide such composites with improved properties
such as greater strength, higher electrical and thermal conductivity and toughness. Polymeric
composites with carbon fibers are used to make parts for automobiles, airplanes, parts for
electromagnetic shielding or for support for catalytic particles. Several methods are known in the
art for producing carbon fibers.
A first method involves dehydrogenating and graphitizing organic polymer filaments by
heating them in a suitable atmosphere to make continuous carbon fibers with diameters typically
between 1 and 5 μm. A second method involves producing discontinuous carbon fiber segments
by vaporizing a hydrocarbon and then with a carrier gas contacting the hydrocarbon vapor with a
suitable metal catalyst.
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
I
Vol-03, Issue-04, April 2015
This type of carbon fiber is known as "vapor grown carbon fiber" or VGCF. Typical VGCF
consists of fibers a few μm in diameter with lengths ranging from a few microns to several
centimeters. The catalyst can be either particulate or can be produced in the gas phase by
decomposition of a suitable metal-containing precursor. Carbon fibers with diameters in the range
of 6-10 μm posses high elastic moduli and strengths and are used as a reinforcing material in epoxy
and polyster resins for manufacture of high stiffness composites.
2. CLASSIFICATION AND MATERIALS IN CARBON FIBERS
Carbon fibers are classified by the tensile modulus of the fiber. Tensile modulus is a
measure of how much pulling force a certain diameter fiber can exert without breaking. The
English unit of measurement is pounds of force per square inch of cross-sectional area, or psi.
Carbon fibers classified as "low modulus" have a tensile modulus below 34.8 million psi (240
million kPa). Other classifications, in ascending order of tensile modulus, include "standard
modulus," "intermediate modulus," "high modulus," and "ultrahigh modulus." Ultrahigh modulus
carbon fibers have a tensile modulus of 72.5-145.0 million psi (500 million-1.0 billion kPa). As a
comparison, steel has a tensile modulus of about 29 million psi (200 million kPa). Thus, the
strongest carbon fiber is about five times stronger than steel.
The term graphite fiber refers to certain ultrahigh modulus fibers made from petroleum pitch.
These fibers have an internal structure that closely approximates the three-dimensional crystal
alignment that is characteristic of a pure form of carbon known as graphite.
Raw Materials : The raw material used to make carbon fiber is called the precursor. About 90%
of the carbon fibers produced are made from polyacrylonitrile. The remaining 10% are made from
rayon or petroleum pitch. All of these materials are organic polymers, characterized by long strings
of molecules bound together by carbon atoms. The exact composition of each precursor varies
from one company to another and is generally considered a trade secret.
During the manufacturing process, a variety of gases and liquids are used. Some of these materials
are designed to react with the fiber to achieve a specific effect. Other materials are designed not to
react or to prevent certain reactions with the fiber. As with the precursors, the exact compositions
of many of these process materials are considered trade secrets.
3. THE MANUFACTURING PROCESS
The process for making carbon fibers is part chemical and part mechanical. The precursor is drawn
into long strands or fibers and then heated to a very high temperature with-out allowing it to come
in contact with oxygen. Without oxygen, the fiber cannot burn. Instead, the high temperature
causes the atoms in the fiber to vibrate violently until most of the non-carbon atoms are expelled.
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
I
Vol-03, Issue-04, April 2015
Fig 1: Manufacturing Process
This process is called carbonization and leaves a fiber composed of long, tightly the fibers are
coated to protect them from damage during winding or weaving. The coated fibers are wound onto
cylinders called bobbins. inter-locked chains of carbon atoms with only a few non-carbon atoms
remaining. The operations are Spining, Stabilizing, Carbonizing, Treating surface, Sizing.
Fig 2: CFRP Manufacturing Process
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
I
Vol-03, Issue-04, April 2015
Fig 3. Flow chart of CF Procesor
4. DIFERENT MATERIAL PROPERTIES
Table 1.Potential Light Weight Materials
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
I
Vol-03, Issue-04, April 2015
Fig 4. Tensile and Compressive Strain
Table 2. Tensile Strength
Material
Fibre Strength
Laminate Strength
E Glass
3450
1500
Carbon Fiber
4127
1600
Kevlar
2757
1430
Epoxy
N/A
12-40
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
I
Vol-03, Issue-04, April 2015
Weight per Unit Volume or Density of Carbon fibre, Kevlar, and E Glass
Table 3. Density and Strength to Weight Ratio
Material
Density
StrengthFibre
Laminate of
toStrength Strength Laminate
Weight
grams/cc
E Glass
3450
1500
2.66
564
Carbon Fiber
4127
1600
1.58
1013
Kevlar
2757
1430
1.44
993
Epoxy
N/A
12-40
1-1.15
28
Table 4. Modulus of Elasticity
Material
Young's Modulus
E Glass
30-40
Carbon Fiber
125-181
Kevlar
70.5-112.4
Epoxy
3
Table 5. Comparison chart of Glass, Aramid and Carbon Fibre
Cost
Weight to Strength
Ratio
Tensile Strength
Compressive
Strength
Stiffness
Glass
Aramid
Carbon Fibre
Excellent
Fair
Poor
Poor
Excellent
Excellent
Excellent
Excellent
Excellent
Good
Poor
Excellent
Fair
Good
Excellent
Excellent
Good
Excellent
Fair
Fatigue Resistance Good-Excellent
Abrasion
Resistance
Fair
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
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Vol-03, Issue-04, April 2015
Excellent
Poor
Excellent
Poor
Poor
Excellent
Excellent
Fair
Excellent
Good
Fair
Good
Resin Adhesion
Excellent
Fair
Excellent
Chemical
Resistance
Excellent
Fair
Excellent
Sanding/Machining
Conductivity
Heat Resistance
Moisture
Resistance
Fig 5. CF Manufacturing Cost
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ISSN No: 2309-4893
International Journal of Advanced Engineering and Global Technology
I
Vol-03, Issue-04, April 2015
5. CONCLUSION
Despite the carbon fibers amorphous structure, it is still a dependable material that can be
used for structural engineering applications, and it is currently used in the military, aircraft, auto,
and sports industry. Since the cost of carbon fibers are dropping, new areas where they can be
profitably be applied will open up; after all, their material properties are highly sought after—high
Young’s modulus of elasticity, high tensile strength, low weight, high formability, etc.
Furthermore, if the manufacturing procedures can be improved to achieve the full development of
aromatic carbon rings, the carbon fibers’ material properties will be further enhanced.
If I had more time and money, I would like to continue this exploration of the carbon fibers’
inside. I have also learned the importance of proper sample preparation for the tests that will be
preformed. Experimental results and model calculations have shown that these materials have the
potential for useful performance in important extended-life applications. Current issues include
coating quality and reproducibility, coating spallation, and chemical effects associated with the
borate glasses that are needed to seal cracks in the outer coatings.
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International Journal of Advanced Engineering and Global Technology
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