2. Carbonisation
3. Surface Treatment
4. Sizing
1. Oxidation
The first stage is where PAN fibres are heated to 300°C. During this stage hydrogen evolves from the fibres and adds oxygen, which is less volatile. The polyacrylonitrile is also changed from a strand structure to a cyclic structure.
2. Carbonisation
This step incorporates heating the fibres to 3000°C in an inert atmosphere.
The resultant is almost 100% Carbon.
The temperature the fibres are heated to will determine the quality of the resultant fibres.
There are four grades of carbon fibre. These are as follows:
GRADE Temperature HeatedTo (°C) Modulus of Elasticity (Gpa)
Low Modulus To 1000 To 200
Standard Modulus 1000 to 1500 200 to 250
Intermediate Modulus 1500 to 2000 250 to 325
High Modulus 2000+ 325+
3. Surface Treatment
The third step in the process involves forming chemical bonds to the carbon surface in order to give better cohesion to the resin system of the composite.
4. Sizing
In the last process, a neutral finishing agent is used to protect the fibres from further processing and to act as an interface to the resin system of the composite. The finishing agent is usually epoxy.
Uses / Significance To Society:
There are many uses for carbon fibre. The main use for carbon fibre is to give a strong material that is lightweight. This is very practical for use in the aerospace industry, which involves the building of aircraft and space shuttles. Formula One and INDY cars are using carbon fibre shells for the bodies of their racing cars.
The new types of golf drivers are now being typically made from carbon fibre (graphite) with a filling of foam or honeycomb to give the driver head increased strength. This allows the golf ball to be driven further than with the more heavy wooden drivers.
The hybrid composite fibreglass, is a material which is practical in the building of insulations. Ice chests and house insulation are now being typically made from fibreglass.
Fishing rods are being made of carbon fibre as well as the fishing line. Old style fishing line for heavy-duty fishing was large in radius and hence had lots of drag. New style fishing line made of carbon fibre is about half the radius and therefore has a lot less drag, allowing fishermen to do the same job with a lot less effort.
Evaluation of Significance to Society:
The use of carbon fibre in many products has become integral with the growing demand for lightweight products that are easy to use and have the strength to support heavy-duty applications. Carbon fibre is only a fraction of the weight of high tensile steel and as shown in the table it has an outstanding strength.
Standard Grade Carbon Fibre High TensileSteel
Tensile Strength (Gpa) 3.5 1.3
Tensile Modulus (Gpa) 230 210
Density (g/cm3) 1.75 7.87
Specific Strength (Gpa) 2.00 0.17
Carbon fibre is also valuable in hybrid composites as many of the composites carry special properties for use in many applications such as fibreglass which is needed for insulation.
At present the significance of carbon fibre is very important as it is one of the substances known to man with the greatest strength to weight ratio. There are a great number of applications that use carbon fibre because of its incredible properties. Aircraft and Indy cars have gained extra speed and efficiency by using the lightweight carbon fibre materials. Products such as golf drivers and fishing lines made from carbon fibre need less effort to achieve the same or better results than those made from materials such as wood or nylon. Lightweight prostheses made from carbon fibre are more manageable than the heavier wooden versions.
Looking at carbon long term, it would be most probable to say that another substance with a greater strength to weight ratio will be developed. Whether or not that substance would be feasible as far as cost and availability would be hard to predict. It is however possible to say that the demand for high strength to weight ratio products will increase with time.
Conclusions:
Carbon fibre is an extremely practical material with many applications. The need for carbon fibre in today’s society is crucial because there is a great demand for high strength in products but at a fraction of the weight of high tensile steel.
The use of carbon fibre in materials has produced products that are lightweight, strong, manageable and efficient.
Bibliography
Kelly, V. 2002, Carbon Fiber [online], Vince Kelly. Available: <http://www.geocities.com/CapeCanaveral/1320/> [Accessed 27th October 2002]
Sabin, D. 2001, ‘Carbon Fibre in Sports Cars’, Comparing of fibre materials [online]. Available: <http://homepage.ntlworld.com/d.sabin/compare.htm>
[Accessed 27th October 2002]
Sabin, D. 2001, ‘Carbon Fibre in Sports Cars’, Production process of Carbon Fibre [online]. Available: <http://homepage.ntlworld.com/d.sabin/howmade.htm>
