ABSTRACT
The term “composite materials” signies that two or more materials are combined on a macroscopic scale to form a new useful material. The combinations are among any two or more of the known material families, i.e., metals, ceramics, and polymers. The key is the macroscopic examination (by the naked eye or at low magnication) of the new material to identify its constituents. This differentiates composites from other combinations such as alloys, where different constituents come together on the microscopic scale, and the material is macroscopically homogeneous, i.e., components cannot be distinguished by the naked eye. The main objective of a composite material is that it utilizes the most distinguished qualities of its constituents to produce a material with the characteristics needed to perform design requirements. The most signicant characteristics of composites are the strength-to-weight ratio and the stiffness-to-weight ratio, which can be several times greater than steel or aluminum. Other improved properties include fatigue life, toughness, wear resistance, corrosion resistance, appearance (aesthetic aspect), thermal conductivity or insulation, and acoustic insulation. The unique gain of the composites is the possibility of achieving combinations of properties that are not achievable with metals, polymers, or ceramics alone. Nevertheless, it should be noticed that the inherent structure of composites implies that they are heterogeneous and anisotropic.
