Fibre waviness

The waviness introduced into fibres where yarns pass over and under each other in a woven fabric. Crimp reduces the stiffness and compressive strength the fibres can deliver, which is why non-crimp fabrics and unidirectional tapes are preferred for highly loaded laminates.

The main unidirectional load-bearing element running along the length of a wind turbine blade or wing spar, carrying the principal bending loads. Spar caps are typically thick stacks of unidirectional glass or carbon laminate, or pre-cured pultruded planks bonded into the structure.

Intermediate vacuum compaction of a partially completed prepreg stack, carried out periodically during lay-up to remove trapped air and seat the plies before further layers are added. Regular debulks reduce wrinkling, bridging and final void content, especially on curved tooling.

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.