What is a composite?

A composite is a material which is made up of two or more distinct (i.e. macroscopic, not microscopic) materials. A familiar composite is concrete, which is basically made up of sand and cement. Many common materials could be classed as composites, but this website is concerned with fibre reinforced polymer composites.

Polymer composites are plastics within which there are embedded fibres or particles. The plastic is known as the matrix, and the fibres or particles, dispersed within it, are known as the reinforcement.

The reinforcement is usually stiffer than the matrix, thus stiffening the composite material. This stiffer reinforcement will usually be laid in a particular direction, within the matrix, so that the resulting material will have different properties in different directions. This characteristic is usually exploited to optimise the design.

Polymer matrix composites (PMCs) are materials that use a polymer based resin as a matrix material with some form of fibres embedded in the matrix, as a reinforcement. Both thermosetting and thermoplastic polymers can be used for the matrix material. Common polymer composite thermosetting matrix materials include polyester, vinyl ester and epoxy. Polymer composite thermoplastic matrix materials include PEEK, PEI and PPS. Reinforcements include glass, carbonand aramid fibres.