Glass-Reinforced Plastic (GRP), is a composite material or fiber-reinforced plastic made of a plastic reinforced by fine fibers made of glass. Like graphite-reinforced plastic, the composite material is commonly referred to by the name of its reinforcing fibers (fiberglass). The plastic is thermosetting, most often polyester or vinylester, but other plastics, like epoxy (GRE), are also used. The glass is mostly in the form of chopped strands mat (CSM), but woven fabrics are also used.
As with many other composite materials (such as reinforced concrete), the two materials act together, each overcoming the deficits of the other. Whereas the plastic resins are strong in compressive loading and relatively weak in tensile strength, the glass fibers are very strong in tension but have no strength against compression. By combining the two materials together, GRP becomes a material that resist well both compressive and tensile forces. The two materials may be used uniformly or the glass may be specifically placed in those portions of the structure that will experience tensile loads.
GRP is manufactured in sheet form. GRP is proven roofing material that has been used on millions of square meter of roof throughout the various European countries. It is constructed from a single ply GRP laminate which is applied in situ to good quality ply or OSB3 decking.