Composite material

From Freepedia

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, Dyneema 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, transferring load from broken fibers to unbroken ones and between fibers that are not oriented along lines of tension. Also, unless the matrix chosen is especially flexible, it prevents the fibers from buckling in compression. Some composites use an aggregate instead of, or in addition to, fibers.

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

Composite materials can be divided into two main categories normally referred to as short fiber reinforced materials and continous fiber reinforced materials. Continous reinforced materials will often constitute a layered or laminated structure.

Shocks, impact, loadings or repeated cyclic stresses can cause the laminate to separate at the interface between two layers, a condition known as delamination. Individual fibers can seperate from the matrix e.g. fiber pull-out.

Examples of composite materials:

• Fibre reinforced plastics:
  • Classified by type of fiber:
    • Wood (cellulose fibers in a lignin and hemicellulose matrix)
    • Carbon-fibre reinforced plastic or CRP
    • Glass-fibre reinforced plastic or GRP (informally, "fiberglass")
  • Classified by matrix:
    • Thermoplastic Composites
      • long fiber thermoplastics or long fiber reinforced thermoplastics
      • glass mat thermoplastics
    • Thermoset Composites

• Metal matrix composites or MMCs:
  • Cermet (ceramic and metal)
    • White cast iron
    • Hardmetal (carbide in metal matrix)
  • Metal-intermetallic laminate
• Ceramic matrix composites:
  • concrete
  • Reinforced carbon-carbon (carbon fibre in a graphite matrix)
  • Bone (hydroxyapatite reinforced with collagen fibers)
• Organic matrix/ceramic aggregate composites
  • Mother of Pearl
  • Syntactic foam
  • Asphalt concrete
• Chobham armour (see composite armour)

• Engineered wood
  • Plywood
  • Oriented strand board
  • Wood-polymer lumber (recycled wood fiber in polyethylene matrix)
  • Pycrete (sawdust in ice matrix)