Composite materials (or composites for short) are engineering materials made from two or more components. One component is often a strong fibre such as fiberglass, quartz, kevlar or carbon fibre that gives the material its tensile strength, while another component (called a matrix) is often a resin such as polyester or epoxy that binds the fibres together and (most often) renders the material stiff and rigid. Some composites use an aggregate instead of, or in addition to, fibers.

In terms of stress, any aggregate serves to resist compression, any fibers serve to resist tension, and the matrix serves to resist shear.

Examples of composite materials:

• Fibre reinforced plastics:
  • Wood (cellulose fibers in a lignin and hemicellulose matrix)
  • Glass-fibre reinforced plastic or GRP (informally, "fiberglass")
  • Carbon-fibre reinforced plastic or CRP
• Metal matrix composites or MMCs:
  • cermet (ceramic and metal)
    • White cast iron
    • Hardmetal
• Ceramic matrix composites:
  • concrete
  • Reinforced carbon-carbon (carbon fibre in a graphite matrix)

• Chobham armour (see composite armour)
• Plywood
• Weatherbest