CF
Definition: A group of fibrous materials comprising essentially elemental carbon. They may be prepared by pyrolysis of organic fibers, the most widely used method. Carbon and graphite fibers are used interchangeably. However, PAN base carbon fibers are 93-95% carbon by elemental analysis, whereas graphite fibers are usually 99 + % carbon. The basic difference is the temperature at which the fibers are made or heat treated. PAN-base carbon is produced at about 1315°C (2400°F), while the high modulus graphite fibers are graphitized at 3450°C (5450°F). Graphite fibers are the stiffest fibers known and have very high strengths and moduli which remain constant at high temperatures. The graphite fibers themselves are composites in that only part of the carbon present has been converted to graphite in tiny crystalline platelets specially orientated with respect to the fiber axis. The higher the graphite content, the stiffer the fiber, but the lower the strength. Less expensive pitch based fibers are an alternative to graphite fibers. Carbon and graphite fibers have been used as reinforcements for ablative plastics and for reinforcement for light-weight, high-strength, and high-stiff-ness structures. The high-stiffness and the high-strength of fibers depends on me degree of preferred orientation. Carbon fibers may also be produced by growing single crystals in a carbon electric arc under high pressure, inert gas, or by growth from a vapor state by thermal decomposition of a hydrocarbon gas.