1. Introduction

Composites have existed in nature right from the evolution of life on Earth. Wood is the finest example of natural composite in which cellulose is reinforcement and lignin is matrix. The combination of bones and musculature is another example of a natural composite where bones are reinforcements and muscles are the matrix. Similarly, in orthopods, the exoskeletal body is reinforcement, and interior soft tissues are matrix. By definition, composites are the materials/structures that have two or more physically distinct constituent phases, and the resultant properties of these materials/structures are superior to the properties of its constituent phases. These phases are primarily reinforcement and matrix and are separated by a distinct interphase. Interphase has a different combination of properties from those of constituent phases. In hybrid composites, different types of reinforcements are used. A composite material also may be defined as the heterogeneous material that consists of two or more constituent materials which do not lose their characteristics. This combination of constituent materials results in new desirable properties. Normally, the constituents (reinforcement and matrix) can be physically identified along with the interface, which also generally controls the properties of the composites. The constituents can be organic, inorganic, or metallic in the form of particles, rods, fibres, plates, foams, etc., and they do not dissolve or merge completely into each other [1, 2].