How is carbon fiber made?
Carbon fiber is considered to be every engineer's dream material because it is lightweight while being extremely durable. It consists of thousands of parallel strings. These threads can be twisted or woven into carbon fiber composites. Carbon fiber is an extremely valuable material because it is five times stronger than steel.

For the manufacture of carbon fibers, plastic PAN fibers are used. It consists of thousands of filaments thinner than a human hair. They chemically alter it to form chains of carbon atoms, which in turn are used in the final product. There are special machines that can arrange thousands of these fibers. After the machine, the fibers pass through an oxidation oven for a few minutes.

The temperature in the oven is about 480 degrees Fahrenheit. Due to this temperature, the fibers absorb oxygen molecules from the air. This process rearranges the atomic structure of the fibers, making them resistant to heat. As the fibers oxidize, they change color and turn black. After oxidation, they are ready for the next process, carbonization.

The fibers are heated in an oxygen-free gas mixture. Due to this process, non-carbon atoms are expelled. The remaining carbon atoms transform into tightly bound crystals that run parallel to the length of the fiber. This is where the material gains its strength. The fibers are then run through a charged water bath which edges the fiber surfaces so they will absorb the resin better.

Next, a light primer coat of resin is applied to strengthen the chemical bonding of the fibers to the molding resin. After this process, the fibers are either woven into carbon fiber fabrics or mixed with resin to form products. It can be a roll of continuous fiber strands, woven fabrics of reticulated strands and prepreg products, semi-finished products ready for use. The use of prepregs is widespread worldwide.

This resin is a formulation of epoxy resin with powdered hardener and accelerator. Workers pour the resin into a film machine, which prints the resin in a thin, wet layer onto paper. At the same time, another machine organizes 200 to 300 carbon fibers into a carbon fiber web. The thickness of the web determines the thickness of the prepreg.

Typically, two rolls of resin coated paper are mounted on the resin impregnating machine. The heating element heats the web as it enters to facilitate resin absorption. Then, the heated carbon fiber mesh is sandwiched between two sheets of resin-coated paper. Thanks to high-pressure heated rollers, the resin penetrates into millions of carbon fiber filaments.

Where it cools, the liquid resin turns into a gel so that at the next station, the paper can be removed. In the next station, the top of the prepreg sheet is covered with a Mylar film. Afterwards, the sheet is wound into a roll. In the factory's laboratory, technicians perform quality control tests on prepreg samples. Such testing ensures that carbon fiber has optimum strength, durability and heat resistance.

Needless to say, manufacturers around the world employ various techniques that are company secrets, but broadly speaking, the aforementioned carbon fiber manufacturing process is the one everyone follows.