GRP, colloquially fiberglass, glass fiber-reinforced plastic - are all designations for a fiber-plastic composite made of a castable plastic (matrix) and glass fibers, whereby the fibers are embedded in the matrix. Glass fibres are thin threads drawn from molten glass, the matrix usually consists of duroplastic polyester or epoxy resin.
While in other contexts the special optical properties of glass fibers are used for data transmission, GRP is concerned with the mechanical properties resulting from the bond between fiber and plastic. Although the material is less rigid than CFRP or steel, for example, it combines high breaking strength with flexibility and elasticity - to put it more simply: You can bend a GRP rod in very tight radii and load it without it breaking. In addition, glass fibre reinforced plastics are corrosion and weather resistant and have a good electrical insulation effect.
GFK is produced depending on the application: The fibres are further processed into textile, regularly arranged fabrics or scrims with irregular arrangement and embedded in a plastic. For the production of rods, tubes and profiles, the fibres are usually bundled into a thicker strand (roving). This fibre strand is then impregnated with a plastic resin, heated and drawn through an extrusion die, then cured. The fibres run unidirectionally (all in the same direction).
Due to their flexibility, GFKs are used in the manufacture of springs and sports equipment such as bows and fishing rods. In igloo tents, they are optimally used to stabilize the curved shape. They are also used in kite construction and in other (laminated) forms in boat and vehicle construction (most of them are certainly already in the outdoor pool through the narrow channel of a giant slide made of GFK). Fibreglass rods are often used to tailor wide, wide tire skirts in order to give the garment a stable, flexible and hopefully still wearable frame.
GRP parts can be sawn with a hacksaw or a circular saw; the problem is that the ends fray and post-processing does not significantly improve the interface. A band saw with diamond-studded band saw blade is ideal, i.e. a very hard, relatively closed band saw blade. Alternatively, a fine boring grinder with (diamond-coated) cutting disc is recommended.
The material is best bonded with a two-component epoxy-based adhesive. For pipe or rod extensions, however, an (additional) internal or external mechanical connection in the form of a sleeve or connecting piece is always recommended.
GRP semi-finished products are easy to paint, but, as is common practice, they should be lightly sanded, made dust-free and only then painted.