A composite material is a mixture of at least two separate phases which are mixed or bonded together to obtain superior mechanical properties compared to those of its constituents. Each phase in the composite structure retains its identity and maintains its properties, however as a joint unit, the composite material provides better mechanical properties including stiffness, strength and hardness. Composites are generally classified according to the matrix material (i.e the main phase),
1) Metal Matrix Composites
2) Polymer Matrix Composites
3) Ceramic Matrix Composites
Typical examples include; aluminium reinforced with silicon carbide or carbon fibers, nylon reinforced with glass fibres, and ceramic materials reinforced with fibers of silicon carbide.