Due to their properties, glass fibres are the most widely used material for fibre reinforcements. Their good tensile and compressive strength, as well as their high modulus of elasticity, allow for application as mechanically and thermally stressed composites. They are divided into the two types of direct rovings and assembled rovings.
In the case of direct rovings, tension-like filaments are first drawn from the glass melt, cooled and provided with a size. The size serves as a binding agent in that the individual filaments are held together in the bundle, influences the cutting ability and is also matched to the resin matrix, which ensures optimum adhesion between resin matrix and glass fibre reinforcement. Direct rovings are used in the winding and pultrusion processes and in the production of woven fabrics and non-crimp fabrics. They are available starting at a weight of 300 tex.
On the other hand, in the case of assembled rovings of filaments, "strands" are formed which consist of a few hundred very weakly bound, parallel filaments. These are finally combined into a bundle, the roving. Due to the weak bond between the continuous fibres, assembled rovings are ideally suited for fibre injection or for producing cut glass or glass fibre mats.