Composite Materials

Abstract

Composite materials are multiphase materials obtained by artificial combination of multiple component materials, for example, a composite with continuous carbon fibers (reinforcement) that are bound by a polymer (matrix or binder). The reinforcement is commonly fibers or particles. Composite materials with continuous fibers (preferably aligned to achieve a high volume fraction) are particularly attractive for their high modulus and strength. The matrix can be polymer (thermosetting or thermoplastic), cement (silicate), metal (eg, aluminum), carbon (eg, graphite), ceramic (eg, silicon carbide), or hybrid (eg, carbon + silicon carbide). Polymer matrix materials are attractive for their low density and low cost. Cement matrix composites such as concrete (which has sand and stones as reinforcement) are even lower in cost. Metal matrix, carbon matrix, and ceramic matrix composites are superior in their ability to withstand elevated temperatures and are also attractive for their low thermal expansion, but their fabrication costs are high. In addition, metal matrix composites are attractive for their high electrical/thermal conductivity and creep resistance. Continuous carbon fiber–carbon matrix composites (carbon–carbon composites) are dominant for high‐temperature lightweight structures, in spite of their tendency to be oxidized at elevated temperatures in the presence of oxygen. Continuous ceramic fiber–ceramic matrix composites (ceramic–ceramic composites) are superior to carbon–carbon composites in the ability to withstand high temperatures, but they are more expensive. The structure, fabrication methods, properties, and applications of various types of composites are covered. Emphasis is on polymer matrix composites with continuous fiber reinforcement due to their wide utilization in lightweight structures. Theories of reinforcement are introduced for unidirectional laminated composites.