Attributes and Production: GRP, the colloquial version `fibreglass´, glass fibre reinforced plastic – these are some of the names for a fibre and plastic composite made from a combination of pourable plastic (the matrix) and glass fibres whereby the fibres are embedded into the matrix. Glass fibres are thin threads that are pulled from molten glass; the matrix usually consists of duroplastic polyester or epoxy resin.
Although in other fields the special optical attributes of glass fibres are used for data transfer, in the case of GRP it is the mechanical attributes that come about as a result of combining the fibres with plastic that are important. This material is in fact less stiff than, for example, CRP or steel but it makes up for that by virtue of its high breaking strength combined with excellent flexibility and elasticity; simply put, it can be bent in very tight radii and put under stress without it breaking. In addition, glass fibre reinforced plastic is corrosion and weather resistant and has great electrical insulation attributes.
Depending on intended use, GRP is produced in different ways: The fibres are processed into textile-like, uniformly arranged weaves or, alternatively, into irregularly arranged layers (non-woven) and embedded in a plastic. When being used in the production of rods, tubes and profiles, the fibres are usually bunched into thicker strands (rovings). These fibre strands are then soaked with a plastic resin, heated and forced through an extrusion nozzle, whereupon they are cured. The fibres in this latter case are all aligned in the same direction (unidirectional).
Applications: Because of their flexibility, GRPs are used in the production of such things as springs and sports equipment, like archery bows and fishing rods. They also serve as the perfect stabilizing device for the arched shape of igloo-type tents. Kites are another area of use along with, in different (laminated) form, the making of boats and cars (surely many of you have experienced hurtling down the narrow chute of a giant waterslide at the local pool). Tailors also put fibreglass rods to use when making expansive crinolines in order to provide clothing with a sturdy, flexible and hopefully wearable scaffolding.
Treatment: GRP can be cut with a bow saw or a circular saw; there is the problem, however, that the ends will tend to fray to such an extent that even remedial measures will not really make it better. A band saw with a diamond band saw blade is the ideal tool to work with; i.e. a very hard band saw blade with a relatively tight tooth pattern (gulleted edge configuration). A PRECISION DRILL GRINDER with a (diamond coated) CUTTING DISC can also be used with good results.
Best gluing results are achieved when using a two-component epoxy adhesive. When elongating tubes or rods, it is best to employ an (additional) outer or inner mechanical connector like a sleeve or coupler.
GRP semi-finished products can be painted but, as is usually with such work, they should first be sanded and cleaned of dust and dirt before applying the paint.
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