A composite material combines distinct constituent materials so that the resulting material has a useful combination of properties that the constituents do not provide alone.

A common composite contains a continuous matrix surrounding a dispersed reinforcement.

Roles of the constituents

The reinforcement can provide stiffness, strength, wear resistance or another targeted property. The matrix transfers load into the reinforcement, maintains its arrangement and protects it from damage or environment.

Common forms

Composites are often classified by reinforcement geometry:

• particle-reinforced composites;
• short-fibre composites;
• continuous-fibre composites.

They can also be classified by matrix material, such as polymer-, metal- or ceramic-matrix composites.

Tailored properties

Composition, reinforcement fraction, shape and orientation can be changed to tailor mechanical, thermal or electrical behaviour.

This flexibility is also a complication: unlike many homogeneous isotropic materials, composite properties can depend strongly on direction and manufacturing quality.