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Composite materials

A composite material (also called composite) is a material made from two or more constituent materials with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure. The new material may be preferred for many reasons: common examples include materials which are stronger, lighter, or less expensive when compared to traditional materials.

Constituents :

  • A thermoplastic polymer matrix or thermosetting material which brings to the material its shape and cohesion, distributes the stresses and protects the fibers from the environment.
  • Reinforcements, mainly long or continuous fibers (carbon, glass, aramid ...) whose function is to provide strength and stiffness
  • Other components and additives: compatibilizers, UV stabilizers, conductive fillers, flame retardants ...

Today, composites show great vitality and innovations keep emerging. They appear as materials of the future and the process optimization associated with R&D give them a real dynamic.

Matrices properties

Composite matrices are conventionally thermosetting: They are epoxides or phenolic liquid low viscosity resins which cure in an irreversible polymerization cycle and which, therefore, are non-recyclable by melting: especially polyester, vinylester, Epoxy, phenolic, cyanate ester, etc. Thermosetting matrix composites account for about 70% of composites processed in Europe.

The polymeric thermoplastic hardens during cooling. The process of chemical transformation that makes them is reversible. Thermoplastic matrices have a high viscosity and are carried out by fusion. They are PP, PA, PBT, PEI, PPS, PEEK... and grow faster (8% / year) than thermosets.

The main advantage of thermoplastic composites compared to thermosets is that they can be used (and re-used or recycled) in the molten state, but they also have a more flexible matrix which gives them a better shock and impact resistance.