Carbon Fiber..

Carbon fiber are high performance advanced materials which are stronger than steel, stiffer than titanium and lighter than aluminium. Carbon fibers are generally produced by thermal degradation of materials such as viscose rayon, poly acrylonitrile, pitch, resins, methane, benzene etc. Their properties are influenced by the manufacturing techniques employed.
Carbon fibers are generally reinforced in two ways. Carbon fibers reinforced in a light weight matrix such as epoxy resin, polyester resin or polyamide are called carbon fiber reinforced plastics (CFRP). When the carbon fibers are reinforced in a carbon matrix, they are known as carbon fiber reinforced carbons (CFRC).These are otherwise known as carbon-carbon composites.
The application of reinforced carbon fibers can be broadly classified into three:
1) High technology sector including, aerospace, military and nuclear fields
2) General engineering sector including sports, transportation and chemical fields
3) Biomedical sector

In aerospace sector, reinforced carbon fibers are used to make aircraft wings, tail parts and helicopter rotor blades. Due to high thermal conductivity of carbon fibers, they are used as wall material of nuclear fission reactor and to make automobile parts. Due to very high strength and stiffness, carbon fibers are used to make sports goods and racing vehicle bodies. In biomedical sector, carbon fiber is used to make artificial human body parts such as bone plates, ligaments etc. Activated carbon fibers are used for water treatment. In defence sector, carbon fibers are used to make nose tips and head shields of missiles and rockets.

Carbon Fiber Reinforced Polymer (CFRP)

Carbon Fiber Reinforced Polymer (CFRP) is a Polymer Matrix Composite material reinforced by carbon fibers.


The reinforcing dispersed phase may be in form of either continuous or discontinuous carbon fibers of diameter about 0.0004” (10 mkm) commonly woven into a cloth.


Carbon fibers are very expensive but they possess the highest specific (divided by weight) mechanical properties: modulus of elasticity and strength.


Carbon fibers are used for reinforcing polymer matrix due to the following their properties:


    Very high modulus of elasticity exceeding that of steel;


    High tensile strength, which may reach 1000 ksi (7 GPa);


    Low density: 114 lb/ft³ (1800 kg/m³);


    High chemical inertness.


The main disadvantage of carbon (Graphite) fibers is catastrophic mode of failure (carbon fibers are brittle).


The types of carbon fibers are as follows:


    UHM (ultra high modulus). Modulus of elasticity > 65400 ksi (450GPa).
    HM (high modulus). Modulus of elasticity is in the range 51000-65400 ksi (350-450GPa).
    IM (intermediate modulus). Modulus of elasticity is in the range 29000-51000 ksi (200-350GPa).
    HT (high tensile, low modulus). Tensile strength > 436 ksi (3 GPa), modulus of elasticity < 14500 ksi (100 GPa).
    SHT (super high tensile). Tensile strength > 650 ksi (4.5GPa).


Carbon fibers are also classified according to the manufacturing method:


1. PAN-based carbon fibers (the most popular type of carbon fibers).


In this method carbon fibers are produced by conversion of polyacrylonitrile (PAN) precursor through the following stages:


    Stretching filaments from polyacrylonitrile precursor and their thermal oxidation at 400°F (200°C). The filaments are held in tension.


    Carbonization in Nitrogen atmosphere at a temperature about 2200 °F (1200°C) for several hours. During this stage non-carbon elements (O,N,H) volatilize resulting in enrichment of the fibers with carbon.


    Graphitization at about 4500 °F (2500°C).


2. Pitch-based carbon fibers.


Carbon fibers of this type are manufactured from pitch:


    Filaments are spun from coal tar or petroleum asphalt (pitch).


    The fibers are cured at 600°F (315°C).


    Carbonization in nitrogen atmosphere at a temperature about 2200 °F (1200°C).


The most popular matrix materials for manufacturing Carbon Fiber Reinforced Polymers (CFRP) are thermosets such as epoxy, polyester and thermoplastics such as nylon (polyamide).


Carbon Fiber Reinforced Polymers (CFRP) materials usually have laminate structure, providing reinforcing in two perpendicular directions.


Carbon Fiber Reinforced Polymers (CFRP) are manufactured by open mold processes, closed mold processes and Pultrusion method.


Carbon Fiber Reinforced Polymers (CFRP) are characterized by the following properties:


    Light weight;
    High strength-to-weight ratio;
    Very High modulus elasticity-to-weight ratio;
    High Fatigue strength;
    Good corrosion resistance;
    Very low coefficient of thermal expansion;
    Low impact resistance;
    High electric conductivity;
    High cost.


Carbon Fiber Reinforced Polymers (CFRP) are used for manufacturing: automotive marine and aerospace parts, sport goods (golf clubs, skis, tennis racquets, fishing rods), bicycle frames.
Properties of some Carbon Fiber Reinforced Polymer Composites


(Materials Data)


    Epoxy Matrix Composite reinforced by 70% carbon fibers
    Epoxy Matrix Composite reinforced by 50% carbon fibers
    Polyether Ether Ketone B Matrix Composite reinforced by 30% carbon fibers

History of Carbon Fiber:

         Dr. Roger Bacon created the first high performance carbon fibers at the Parma Technical Center outside of Cleveland, OH. The first fibers were manufactured by heating strands of rayon until they carbonized. This process proved to be inefficient, as the resulting fibers contained only about 20% carbon and had low strength and stiffness properties. In the early 1960s, a process was developed using polyacrylonitrile as a raw material. This produced a carbon fiber that contained about 55% carbon and had much better properties. The polyacrylonitrile conversion process quickly became the primary method for producing carbon fibers.

On the 14th January 1969, Carr Reinforcements wove the first ever Carbon fibre fabric in the world.

During the 1970s, experimental work to find alternative raw materials led to the introduction of carbon fibers made from a petroleum pitch derived from oil processing. These fibers contained about 85% carbon and had excellent flexural strength.

Carbon fiber under microscope

On the other hand, Un-isotropic Pitch Type Carbon Fiber is sometimes referred to as "Mesophase Pitch Type Carbon Fiber". This fiber is commonly a continuous fiber (filaments) of 7 - 10 micron meter in diameter with 1.7 - 2.2 g/cm3 of density. There are 1K, 2K, 3K, 6K and 12K as filaments per tow and wide variety of elastic modulus grades from 6 GPa (the lowest) to 953 GPa (the highest), whereas PAN Type Carbon Fiber cannot achieve this range. High Elastic Modulus Type Carbon Fiber (350 GPa -) has excellent processability due to high tensile strength, more than 2.5 GPa, and has been extensively applied for industrial and sports/recreation fields utilizing higher stiffness than iron and light weight (50% or less than iron) as molded composite materials. Applications for Ultra High Elastic Modulus Type Carbon Fiber (600 GPa -) are expanding, utilizing excellent stiffness, equivalent or higher thermal conductivity to metals and lightness in weight.

"Light in weight, Strong and Durable!" Carbon Fibers are nothing but a 21st. century high technology material. The fibers have low specific gravity, exquisite mechanical properties (high specific tensile strength, high specific elastic modulus, etc.) and attractive performances (electric conductivity, heat resistance, low thermal expansion coefficient, chemical stability, self-lubrication property, high heat conductivity, etc.). Those features have been stimulating Carbon Fiber users to develop numerous kinds of applications.

Carbon fiber, stronger than steel, and much lighter. How they make it?

They start off with another polymer, called polyacrylonitrile. They take this polymer, and heat it up. They are not sure just exactly what happens when they do this, but we do know that the end result is carbon fiber. They think the reaction happens something like this: when they heat the polyacrylonitrile, the heat causes the cyano repeat units to form cycles!

Then they heat it again! This time they turn the heat up higher, and our carbon atoms kick off their hydrogens, and the rings become aromatic. This polymer is a series of fused pyridine rings.

Then they heat it...AGAIN! Slow roasting the polymer something more, at around 400-600°C causes adjacent chains to join together.

This expels hydrogen gas, and gives us a ribbon-like fused ring polymer.

But they are not done yet! Next they crank up the heat, anywhere from 600 all the way up to 1300oC. When this happens, our newly formed ribbons will join together to form even wider ribbons.

When this happens, they expel nitrogen gas. On the polymer we get, it has nitrogen atoms along its edges, and these new wide ribbons can then merge to form even wider ribbons.

As this happens, more and more nitrogen is expelled. When we're through, the ribbons are really wide, and most of the nitrogen is gone, leaving us with ribbons that are almost pure carbon in the graphite form. That's why we call these things carbon fibers.

Spools of row Carbon fiber

Carbon fibers, under industrial production now, are classified into PAN-based, pitch-based and rayon-based. Among them, PAN-based carbon fiber is in the largest production and best used in volume. In the beginning of 1970's, commercial production of PAN-based and isotropic pitch-based carbon fibers was started on a large scale. In the latter half of 1980's, anisotropic pitch-based carbon fiber manufacturers broke into the market.

Usage of carbon fiber by itself is not the rule. Commonly, customers apply carbon fibers for reinforcement and / or functionality of composite materials, made with resin, ceramic or metal as matrix. Carbon fibers are extensively applied to a large variety of applications with supreme mechanical characteristics (specific tensile strength, specific modulus) and other characteristics due to carbon matter (low density, low coefficient of thermal expansion, heat resistance, chemical stability, self-lubricity, etc.).

Carbon Fibers, having supreme characteristics, are adopted in wide varieties of uses. Suppliers are able to provide, by using different raw material and applying divergent production processes, wide diversity of the fibers having different specifications.

PAN Type Carbon Fiber A type of the fiber, produced by carbonization of PAN precursor (PAN: Polyacrylonitrile), having high tensile strength and high elastic modulus, extensively applied for structural material composites in aerospace and industrial field and sporting / recreational goods.

PAN Type Carbon Fiber is an aggregation of continuous fiber (filaments), 5 – 7 micron meter in diameter with 1.74 - 1.95 g/cm3 of density, generally. Products with various filaments, such as 1K (1000 filaments), 3K (3000 filaments), 6K (6000 filaments), 12K (12000 filaments) and 24K (24000 filaments), referred to as "Regular Tow" or "Small Tow", have been used in large quantity for aircrafts and sports/recreational fields, making good use of low density, high specific tensile strength and high specific elastic modulus. PAN fibers have been undertaken a role for market expansion of carbon fibers.

Large Tow, extra-40K, even though slightly lower tensile strength is mainly used for industrial fields as a relatively inexpensive material, along with Regular Tow. PAN type carbon fibers are classified into Standard Elastic Modulus Type (- 240 GPa), Intermediate Elastic Modulus Type (- 300 GPa) and High Elastic Modulus Type (350 GPa -).

Pitch Type Carbon Fiber Another type of the fiber, produced by carbonization of oil/coal pitch precursor, having extensive properties from low elastic modulus to ultra high elastic modulus. Fibers with ultra high elastic modulus are extensively adopted in high stiffness components and various uses as utilizing high thermal conductivity and / or electric conductivity.

Regarding Pitch Type Carbon Fiber, there are continuous type and discontinuous type, based on respective spinning process.

Pitch Type Carbon Fiber is also classified into Isotropic Type (hardly-graphitizability) and Un-isotropic Type (easy-graphitizability), based on respective raw pitch. Isotropic Pitch Type Carbon Fiber is commonly a discontinuous fiber of 12 - 18 micron meter in diameter with 1.6 g/cm3 of density and has the properties of low modulus (- 40 GPa), strength and thermal conductivity due to its weak structural orientation of carbon atoms and underdeveloped graphite crystallinity. With its competitive cost, Isotropic Pitch Type Carbon Fiber is extensively applied for industrial fields due to light weight, chemical stability, heat resistance and abrasion characteristic.

Carbon Fiber

Carbon fiber (alternately called graphite fiber) is a polimer (made from another polymer, called polyacrylonitrile, by a complicated heating process) which is a form of graphite material consisting of extremely thin fibers about 0.005-0.010 mm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in microscopic crystals (hexagonal aromatic rings) that are more or less aligned parallel to the long axis of the fiber. The crystal alignment makes the fiber incredibly strong for its size. Several thousand carbon fibers are twisted together to form a yarn, which may be used by itself or woven into a fabric. Carbon fiber can be combined with epoxy and wound or molded to form composite materials such as carbon fiber reinforced plastic (also referenced as carbon fiber) to provide a high strength to weight ratio material. The density of carbon fiber is also considerably lower than the density of steel making it ideal for applications requiring low weight. The properties of carbon fiber such as high tensile strength, low weight, and low thermal expansion make it very popular in aerospace, military, and motorsports along with other competition sports. The unique appearance of carbon fiber also makes it popular for stylistic purposes.

These fibers are not used by themselves. Instead, they're used to reinforce materials like epoxy resins and other thermosetting materials. We call these reinforced materials composites because they have more than one component.

Carbon fiber Specific elastic Modulus Carbon Fatique resistance 

Carbon fiber reinforced composites are very strong for their weight. They're often stronger than steel, but a whole lot lighter. Because of this, they can be used to replace metals in many uses, from parts for airplanes and the space shuttle to tennis rackets and golf clubs.