The best impact performing helicoidal configurations are capable of diffusing damage at sub-critical levels through the formation of matrix cracks, helicoidal delaminations and stable fibre failure.
Delaminations tend to be distributed helicoidally through-the-thickness of the laminate rather than being localised at a few ply interfaces.
The design of helicoidal laminates to resist Low Velocity Impact (LVI) impacts should be driven by the correct combination of pitch angle and number of plies for a given fiber type, resin properties and ply thickness.
The outstanding capability of thin-ply helicoidal CFRP laminates to withstand delamination damage through sub-critical damage diffusion leads to a residual Compression After Impact (CAI) strength similar to the one of conventional Quasi-Isotropic (QI) laminates. This is achieved with only 2.6% of the fibre oriented along the loading direction during compression against the much higher proportion of 0°-plies (26%) of the conventional QI laminates.