Areal weight

The proportion of a composite's volume occupied by fibre, a key measure of laminate quality and the main driver of stiffness and strength in the fibre direction. It is determined by methods such as resin burn-off, acid digestion or image analysis of polished sections.

The metric unit of linear density for fibres, strands and yarns, defined as the mass in grams of one kilometre of the product. Glass rovings and yarns are specified by tex, with higher values indicating heavier strands.

A non woven glass reinforcement made from chopped strands distributed randomly and held with a powder or emulsion binder that dissolves in styrene based resins. It gives roughly equal in plane properties in all directions, wets out readily by hand lay up and is the standard reinforcement in GRP flat roofing laminates. It is specified by areal weight.

A composite element built up from multiple bonded layers (plies) of reinforcement and matrix, consolidated and cured so that they act as a single structural material. Its stiffness and strength depend on the fibre orientations and stacking sequence of the plies.