Woven glass fibres. Coloured scanning electron micrograph (SEM) of glass fibres that have been woven into a sheet. Glass fibre sheets are used for reinforcing plastics. They are laid inside a mould and are impregnated with a plastic resin. When dry the finished material is known as a glass fibre reinforced plastic (GRP), or simply fibreglass. GRP is thermosetting (malleable before curing to a stronger form through the addition of energy) and most often uses either polyester or vinylester. The resulting materials are hard, strong and light, and are used in the construction of aircraft, cars and yachts. Magnification: x35 when printed 10 centimetres wide.