Part (a): Describing how the base raw material is turned into a usable carbon fiber
- Precursor selection: The first step is to choose the right precursor material, which is typically PAN (polyacrylonitrile). PAN is a synthetic polymer that can be converted into carbon fiber through a high-temperature process.
- Oxidation: The PAN precursor is then oxidized in air at temperatures between 200°C and 400°C. This process removes some of the hydrogen and nitrogen atoms from the PAN chains, making them more rigid and stable.
- Carbonization: The oxidized PAN is then carbonized in an inert atmosphere at temperatures between 1000°C and 2000°C. This process drives off the remaining non-carbon atoms, leaving behind a highly ordered structure of carbon atoms.
- Surface treatment: The carbon fibers are then treated with a sizing agent to improve their adhesion to resin and other materials.
Part (b): Describing how the fibers produced in part (a) are turned into a usable product
- Layup: The carbon fibers are arranged in a mold or on a mandrel in the desired shape of the final product. This process is called layup.
- Resin infusion or impregnation: Resin is then infused or impregnated into the fibers. This can be done through vacuum bagging, autoclave curing, or other techniques.
- Curing: The resin is then cured, typically under heat and pressure. This process converts the resin from a liquid to a solid, binding the fibers together and forming the final composite product.
- Finishing: The cured product may then be machined, painted, or coated to meet the specific requirements of the application.
Part (c): Explaining how the internal structure of carbon fiber gives it its unique strength properties
The unique strength of carbon fiber comes from its highly ordered internal structure. Each carbon fiber is made up of millions of carbon atoms arranged in a hexagonal lattice. This strong and stiff arrangement of atoms gives carbon fibers a very high tensile strength (strength under pulling forces) and a high modulus of elasticity (resistance to deformation).
In addition to its strong internal structure, carbon fiber is also very lightweight. This combination of high strength and low weight makes carbon fiber an ideal material for many marine applications, where weight savings and high performance are essential.