Carbon fibre is literally a fibre made of carbon. The carbon content is 90% or more for carbon fibres of standard modulus of elasticity and virtually 100% for carbon fibres of high modulus of elasticity. Nitrogen is the primary element other than carbon.
Carbon fibre is produced by baking PolyAcryloNitrile (PAN) fibre, pitch fibre or other organic fibre in an inert atmosphere to dissociate elements other than carbon. At least 90% of commercially available carbon fibres are PAN carbon fibres made of PAN fibre, because PAN fibre is better than pitch carbon fibre in terms of the balance of performance, cost, ease of use, etc.
The two key features of carbon fibre is it's strength and lightness of weight. Carbon fibre has various other characteristics such as not failing due to fatigue, not rusting, and chemically and thermally stable. It is a highly reliable material whose characteristics are stable over a long period of time even under severe conditions.
Unlike the other fibres which we designate by their linear density (denier), carbon fibres are designated by the number of filaments per fibre. In Stratis we use 6K and 12K ('K' is short for 1,000) so each fibre will have either 6,000 or 12,000 filaments per fibre.
In Stratis we use Ultra High tenacity aerospace grade carbon fibres made in Japan and Korea these are surface treated to promote adhesion to organic matrix polymers.
1. The starting point is a high quality PolyAcryloNitrile (PAN) precursor fibre, which is specifically engineered for carbon fibre production.
2. The PAN precursor is then stretched and tensioned to optimize molecular and structural orientation.
3. In-line quality control of the PAN precursor ensures process continuity and efficiency.
4. The precursor is exposed to hot air, turning it into oxidized polyacrylonitrile fiber.
5. It is carbonized into carbon fibre by exposing it to progressively higher temperatures in a nitrogen-filled oven.
The carbon fibre undergoes final carbonization at more than 1,000-2,000 degrees celsius to establish strength and stiffness, and to ensure it's other material properties.
6. At 2,000-3,000 degrees celsius, graphitization for high modulus types occurs.
7. The carbon fibre is surface-treated or etched to create a surface that will bond effectively.
8. A polymer coating (sizing) is applied to promote fibre-handling characteristics, wet-out and bonding.
9. Continuous fibre is wound onto bobbins.
(Top Image: Carbon Process Table)
(Bottom Image: Close-up of Carbon fibre)