Composites combine the properties of two or more materials (constituents). Any two materials, such as metals, ceramics, polymers, elastomers, and glasses, can be combined to make a composite. They may be mixed in many geometries (particulate, chopped-fiber, woven, unidirectional fibrous, and laminate composites) to create a system with a property profile not offered by any monolithic material. In mechanical design, this is often done to improve the stiffness-to-weight ratio, strength-to-weight ratio, or toughness, while in thermomechanical design, it is to reduce thermal expansion, maximize heat transfer, or minimize thermal distortion. Composites have gained popularity in high-performance products that need to be lightweight yet strong enough to take high loads, such as aerospace structures, space launchers, satellites, and racing cars. Their growing use has arisen from their high specific strength and stiffness when compared to metals, and the ability to shape and tailor their structure to produce more aerodynamically efficient configurations.