A sizeable proportion of the applications of carbon fibers is found in structural composites. These composites comprise a network of fibers providing strength and stiffness and a matrix holding the fiber network together. In the so-called “advanced” or “high-performance” composites, the fibers are silicon carbide, mullite, boron, alumina, and, of course, carbon. These fibers are all competing with each other for a portion of the structural-composite business but, with increasing frequency, carbon fibers are preferred because of their low density, high strength, high modulus, and decreasing cost.
Carbon fibers however are not the universal panacea, and they have several drawbacks which makes them unsuitable for many applications: they are brittle and have low impact resistance and, as a result, are difficult to weave. They also have a coefficient of thermal expansion smaller than most matrix materials, and this mismatch may cause internal stresses in the composite. In addition, they oxidize readily and are not suitable for operation at high temperature in an oxidizing atmosphere.
The matrix of carbon-fiber composites can be a polymer, a ceramic, a metal, or carbon itself (carbon-carbon). These matrix materials are described in following articles.
The carbon-fiber composite industry:
The development of carbon-fiber composites has been rapid in the last twenty years and the industry is now of considerable size and diversity.
In 1991, the worldwide market for these composites was estimated at approximately $700 million, divided into the following sectors, each shown with its approximate share of the business:
Aerospace 70%
Sporting goods 18%
Industrial equipment 7%
Marine 2%
Miscellaneous 3%
Miscellaneous applications include automotive, civil structures, mass transportation, medical products, and other consumer products.
Providing that the cost can be further reduced, the share of non-aerospace segments should increase, especially in the automotive industry.