A Composite material is a compound of two or more materials to combine the performance of both. Even a composite may concern many forms of matter to be combined, the designation is frequently used for the specific typus of fibre reinforces composites.
A fibre reinforced composite is composed from a matrix material and reinforcing fibres. Usually the fibres are from a material with much higher strength and/or stiffness than the matrix material at least in their longitudinal direction, so that the composite shall receive much higher mechanical performance than the bulk material. In some cases also a higher thermal or dimensional stability shall be achieved.
In most cases the matrix material is a plastic material but also metals or ceramics may be applied for very special applications. Reinforcement fibres most frequently used are glass fibres, but the application of extremely stiff carbon fibres is rapidly increasing. In special applications polymeric fibres (aramide fibres, HPPE), ceramic fibres or natural fibres are used.
Very often the general designation 'Composite' is also used for the special version of glass fibre reinforced composite or for the special class of Advanced Composites.
The performance of composites is highly dependent from the adhesion between matrix and reinforcing material. Usually a material can only profit from the reinforcement if it bonds perfect. Very often the reinforcing material requires special treatment or coating (Silan coating) for sufficient adhesion. Plasma treatment of the reinforcement material before forming the composite may improve this adhesion significantly.