Subscribe to our newsletter to receive the latest news and events from TWI:

Subscribe >
Skip to content

Function of fibres and matrix in glass reinforced plastics


Fibres convey structural stiffness and strength to GRP (glass reinforced plastic) materials. The matrix transfers the load between the fibres and also supports them under compression loading. Strength, stiffness and stress-strain properties of composites are a function of the volume fraction of fibres in the section of the GRP, the matrix resin used and the directionality of the fibres with respect to the external loads.

The properties of glass fibres can be tailored by varying the types and amounts of mineral glasses incorporated. Most fibres are based on silica (SiO2) with additions of oxides of calcium, boron, sodium, iron and aluminium. The most common types of glass fibres are:

  • E glass is the most commonly used glass, both in the textiles industry and in composites, where it accounts for 90% of the reinforcement used. E glass fibres have good stiffness, strength, electrical and weathering properties.
  • S glass is more expensive than E glass, has a higher Young's modulus and is more temperature resistant.
  • R glass was developed to have superior fatigue, temperature and humidity resistance. The high technical performance means that R glass is used in aerospace and armaments, and also in sports and leisure and transport.
  • D glass has very good dielectric characteristics and is used in the manufacture of radomes and high performance printed circuit boards.
  • C glass has improved chemical resistance. It is not used in Europe/USA for structural fibres but is used for veils and surfacing layers. In China, C-glass is quite common as a structural fibre in mats and fabrics.

Some of the properties of some types of glass fibre are shown in the Table -

PropertyE glassR glassD glassC glass
Ultimate tensile strength, GPa 3.4 4.4 2.5  
Tensile modulus, GPa 73 86 55  
Elongation to failure, % 4.5 5.2 4.5  
Density, g/cm 3 2.55 2.53 2.14 2.53

For more information please contact us.

For more information please email: