Carbon Fibres.

Essay by jimmygamiasUniversity, Bachelor'sD+, January 2006

download word file, 7 pages 4.0

Carbon Fibres, Carbon-Polymer Composites and Carbon-Carbon Composites

Carbon-Polymer composites consist of carbon fibres, either unidirectional, woven or knitted or 3-Dimensional embedded in a polymer matrix. The polymer matrix can be either a thermosetting resin such as epoxy or a thermoplastic resin such as PEEK. While woven carbon fibre is available un-coated for use in wet lay up manufacturing, the majority of carbon fibre is pre-coated or pre-impregnated (pre-preg) with the polymer. Carbon-carbon composites consist of highly-ordered graphite fibers embedded in a carbon matrix. C-C composites are made by gradually building up a carbon matrix on a fiber preform through a series of impregnation and pyrolysis steps or chemical vapor deposition. C-C composites tend to be stiffer, stronger and lighter than steel or other metals.


The production of carbon based composites begins with the production of the carbon fibers. Carbon fibers are long bundles of linked graphite plates, forming a crystal structure layered parallel to the fiber axis.

This crystal structure makes the fibers highly anisotropic, with an elastic modulus of up to 5000GPa on-axis versus only 35GPa off-axis. Fibers can be made from several different precursor materials, and the method of production is essentially the same for each precursor: a polymer fiber undergoes pyrolysis under well-controlled heat, timing and atmospheric conditions, and at some point in the process it is subjected to tension. The resulting fiber can have a wide range of properties, based on the orientation, spacing, and size of the graphite chains produced by varying these process conditions.

Precursor material is drawn or spun into a thin filament. The filament is then heated slowly in air to stabilize it and prevent it from melting at the high temperatures used in the following steps. The stabilized fiber is placed in an inert atmosphere...