Reinforcements in GRP (Glass-reinforced plastic) work generally refer to loose mats or fabrics, composed of fibre. In certain circumstances, notably in the construction of large moulds, external reinforcements may take the form of a metal or wooden structure bonded to the mould. Use of the work reinforcement in GRP work should generally be read as referring to a mat or fabric suitable for wetting out by means of a resin system.
Reinforcements may be broadly classified by material type, style of composition and surface density.
Let’s go into them with a little more detail –
Material (fibre) types: the most commonly used material is glass fibre, providing an economical and robust reinforcement medium. Carbon fibre is becoming increasingly popular as a secondary stiffening material. Aramid fibre, better known by the trade name as ‘Kevlar’, is also increasingly popular for its toughness properties.
Composition (an aggregate material formed from two or more substances): the most commonly used basic style of reinforcement is that known as Chopped Strand Mat (CSM), always composed of glassfibre strands, usually about 50mm long, held together with a binder (these binders come in two forms Emolution – best used with polyester and Powder bound – best used with Epoxy *Here at Blue Gee, we wouldn’t recommend using an emulsion bound with epoxy. Fibres can be available in ‘tows’ (long bundles of filaments), as uni-directional (UN) mats (majority of fibres run in one direction only, leaving strength in only one direction), or as fabrics.
Surface Density (the thickness of the material): this describes the ‘weight’ or the ‘thickness’ in a more precise term. The surface ‘density’ is generally described in terms of the weight, in Kilograms (kg), of 1 square meter area of the material. *We recommend having 1kg of resin per 1 square meter of material.
An alternative measure, replaced in europe by the metric measure, is that of the Imperial system, measuring in terms of ounces (oz) per square foot (CSM), or ounces per square yard (woven rovings).
There are a very wide variety of fibres used in the industrial GRP work, although as noted – glass, kevlar and carbon are in the most common use. Weaves may be ‘hybrids’, where carbon and kevlar, kevlar and glass etc., are woven to produce composite fabrics.
Thanks for reading!