Interlaminar shear strengthILSS

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.

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.

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.

Mechanical or physical testing of small standardised specimens, known as coupons, cut from a laminate, panel or production sample rather than testing the full component. Coupon results underpin material qualification, design allowables and batch quality control in composites manufacture.

Determination of the proportion of trapped air or volatiles within a cured laminate, typically by density comparison, matrix digestion or burn-off methods, or by image analysis of polished sections. Excess void content degrades interlaminar shear and fatigue performance, so limits are often specified for structural laminates.