The name “glass” refers to a group of materials which are basically undercooled liquids. Glass consists of various oxides which melt to form eutectics. When the molten glass is quickly cooled to room temperature it will turn into a clear rigid solid. This glassy state, unlike the solid state and the fluid state is not thermodynamically stable, but transition rates are so slow that glass is, for all practical purposes, a stable solid material.
Fibreglass is normally supplied as “yarn”, or a “roving”, made up of many fibres. The most common method of making glass fibre is by drawing of molten glass into fine, continuous filaments. The most important variable for the performance of glass fibres in composite materials is the nature of the “size” or “finish” that is applied to the strand during the forming process. The sizing agent determines to a large extent the processing characteristics of the glass fibre products and the conditions of the fibre-matrix interface in the composite material.
Glass fibres are available in different chemical compositions, each exhibiting somewhat different mechanical and chemical properties, and each type designated by a letter of the alphabet.
These fabrics are available as woven fabrics, ie. Plain weave, 2×2 Twill weave, 4 & 8 Harness satin weave; as well as stitched fabrics, ie. Biaxial ± 45°, triaxial 0/90 with ± 45°, quadraxial 0+90 with ± 45°.