Composites are a matrix and reinforcement made up of two constituent materials.
The majority of composites use a polymer matrix material or resin.Reinforcement materials are often fibres but may be ground minerals.
Typically, the strength of the final product is greatly dependent on this ratio of resin and fibre.
Common resins include epoxy, polyester, vinylester and Shape memory polymer (SMP) resin.
Common fibers includes fiberglass, carbon fiber, and Kevlar. Fiber-reinforced composite materials include short fiber-reinforced materials and continuous fiber-reinforced materials which are used in layered or laminated structures.
Composites are anisotropic and characterized by Young's Modulus, Shear Modulus and Poisson's ratio.
Types of Composites:
Thermoplastic resin composite, short fibre thermoplastics, long fibre thermoplastics and long fibre-reinforced thermoplastics.
Reinforced Concrete consists of loose stones (aggregate) held with a matrix of cement with metal cables added to tension the concrete.
Engineered wood composites include Wood fibre board, plywood, oriented strand board, wood plastic composite, Pykrete, Plastic-impregnated or laminated paper or textiles, Arborite, Formica, and Micarta.
Since composites are used to improve stiffness and strength with lighter weight, they are employed in critical applications that include military aircraft, commercial aircraft, aerospace, etc etc. And so testing is more important to confirm design assumptions. Testing is especially important in these applications. The variations in fibres and matrices that are available and the mixtures that can be made with blends leave a very broad range of properties to design for. The best known failure of ceramic matrix composite occurred when the carbon-carbon composite tile on the leading edge of the wing of the Space Shuttle Columbia fractured when impacted during take-off.