As composites, FRPs obtain their properties from the combination of materials that compose them:
- Reinforcement – fibre of organic or inorganic origin, is responsible for mechanical strength. Customarily, the type of reinforcement used is glass fibre, due to its mechanical properties and low cost. In very aggressive environments carbon fibre can be used in those layers of the laminate in contact with that environment (its use is not more widespread because of its high cost compared to glass fibre).
- Matrix – stable thermosetting polymeric resin, which provides resistance to corrosion. The correct behaviour of a component made of FRP when exposed to a corrosive environment is mainly dependent on the selection of the appropriate resin.
In addition to the basic elements described above, other types of additives can be used in the manufacture of FRPs to give certain additional properties, such as:
- Flame retardant
- Charges (to increase rigidity)
- Air release agents
In short, the variety of elements from which these composites can be formed offers a range of possibilities for a final product that meets the most demanding requirements. The basic composition of an FRP laminate is shown in the following figure:
- Gel coat – pure resin layer responsible for a smooth finish on the surface in contact with the mold
- Chemical barrier – layer with high resin content responsible for the integrity of the entire laminate against corrosion
- Structural wall – layer high in fibre responsible for strength and stiffness
- Termination – layer of high resin content responsible for the integrity of the entire laminate against the weather.