When combined with a plastic resin and wound or molded it forms carbon fiber reinforced plastic (often referred to as carbon fiber) which has a very high strength-to-weight ratio, and is extremely rigid although somewhat brittle. However, carbon fibers are also composed with other materials, such as with graphite to form carbon-carbon composites, which have a very high heat tolerance.
Carbon fiber is the common name used to refer to plastic reinforced by a graphite textile.

Carbon fiber is very expensive, but has a fantastic weight-to-strength ratio. Depending on the orientation of the fiber, the carbon fiber composite can be stronger in a certain direction or equally strong in all directions. The properties of carbon fibers, such as high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion, make them very popular, however, they are relatively expensive when compared to similar fibers, such as glass fibers or plastic fibers.
Carbon fibers are usually combined with other materials to form a composite.