In pultrusion fibres or fibre mats are pulled through a guide where they are placed precisely in relation to the desired profile cross section. They are then led through processing equipment where they are impregnated with a matrix material. The combined mixture of fibres and matrix is pulled through heated equipment where the profile is cured in its final geometry. The most commonly used material is glass fibre reinforced polyester (GRP), which has almost twice the strength-to-weight ratio of mild steel.
The profiles are used for load bearing elements such as decks for bridges, cooling tower constructions, and stair case constructions in harsh environments. Other applications are structural parts for wind turbine blades and high insulating window frames.
GRP has good heat insulation and is very resistant to corrosion. The mechanical properties of GRP can be adjusted by changing the amount of fibre used, the fibre placement, and the fibre alignment in the profile.