Editorial Feature

Thermosetting Composites - An Overview

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Thermoset composite materials originate from materials including glass reinforced polyesters or, more generally, fiber reinforced plastics. The high reactivity and ease of impregnation make thermoset composites highly valuable materials within a wide range of industries.

Producing Thermoset Composites

The reinforcement phase of these materials may consist of glass, carbon or aramid fibers in a matrix of resins such as polyesters, vinyl esters, epoxies or phenolics. Prior to impregnation of the fibers, all original materials will begin as either monomeric or oligomeric in nature. The fiber phase may be used in forms such as woven, chopped, strand and continuous filament.

When thermoset composites were originally introduced during the 1950s, glass/polyester composites were the most popular material in this category. However, as advancements in this field have emerged, epoxy-resin-matrix materials have dominated the composites industry. Currently, resin systems, including both polyester and epoxy resins, make up 95% of thermoset composite materials.

Unlike thermoplastic composites, once set, thermoset composites cannot be heated and reshaped; therefore, the possibility for recycling this material is very limited.

Key Properties

  • Low density
  • Corrosion, chemical, strain and flame resistant
  • Good insulating properties
  • High strength-to-weight ratio
  • High stiffness
  • High heat resistance/low heat transfer
  • Highly durable
  • Low shrinkage
  • Stable when exposed to ultraviolet (UV) radiation
  • Non-magnetic
  • Can be formulated to a wide variety of colors, paint and/or metal coatings


Personal Armor

Aramid fiber composites are commonly used for bullet proof vests. Aramid is the material of choice for this purpose because it has excellent abrasion resistance when used in a composite and a strength to weight ratio superior to that of glass.

Automotive Industry

In the automotive industry, glass-reinforced polyester composites can be used for a wide variety of components, including body kits, air defectors and spoilers, battery casings and covers, headlamp housings, bumpers and bumper beams, heat shields for both engines and transmissions, cylinder head covers and pillars.

These materials are often used as a result of their high strength-to-weight ratios, dimensional stability and impact strength, as well as its low coefficient of thermal expansion and low weight.  

Marine Industry

Boat hulls are often made from glass reinforced epoxies as a result of the high strength-to weight-ratio of this material. As is the case with the automotive industry, once a mold is made, many parts can be quite easily produced. Again, this can make fabrication somewhat easier than making a metal hull.

Sporting Goods

A host of sporting goods including surf boards, water skis, fishing rods, tennis racquet frames, snow skis, snow boards, cricket helmets, archery bows and golf-club shafts are made from thermoset composites. The low weight and good strength-to-weight ratios of these materials makes them highly suitable for this specific industry.

Sources and Further Reading

This article was updated on 25th June, 2019.

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