Dry spot

The degree to which liquid resin has penetrated and coated the filaments of a reinforcement, visible in glass fabrics as a change from opaque white to translucent. Complete wet-out is essential to laminate strength, since dry patches act as built-in defects.

A closed-mould process in which dry reinforcement is laid into a mould, sealed under a vacuum bag, and liquid resin is drawn through the fibre stack by vacuum alone. It achieves higher fibre content and lower void levels than open moulding, with much lower workshop emissions.

The proportion of a cured laminate's volume occupied by trapped air or volatiles rather than fibre or resin. Elevated void content degrades interlaminar shear strength and fatigue performance, so it is controlled through debulking, vacuum and cure pressure and checked by testing or non-destructive inspection.

Separation of the plies within a laminate, caused by impact, manufacturing defects, fatigue or moisture ingress. Because it can spread unseen beneath an undamaged surface and sharply reduces compressive strength, delamination is a primary target of non-destructive inspection.