Polymer matrix composites (PMCs) have become one of the important structural engineering materials. This is not only because of the development of high-performance bers such as carbon, polyethylene, and aramid but also because of some new and improved polymer matrix materials. The mechanical properties of polymers in general are inadequate for many engineering applications. In particular, their strength and stiffness are lower than those of metals and ceramics. Hence, there is considerable scope for improving the mechanical properties of these materials by incorporating reinforcements. The resulting composites have the advantage of easy fabrication of polymers with improved properties. PMCs are very common compared to metal and ceramic matrix composites. In general, the processing of polymeric materials does not require high temperatures and pressures. Hence, the fabrication of complex-shaped components is easy with these materials. The problems associated with the degradation of reinforcement during the fabrication are insignicant for PMCs due to lower processing temperatures. Moreover, the equipment required for the fabrications of PMCs are also simpler. Hence, the development in PMCs happened rapidly, and they have become the accepted materials for many structural applications.