Fatigue delamination behaviour of unidirectional carbon fibre/epoxy laminates reinforced by Z-Fiber® pinning

Z-Pin reinforced carbon-fibre epoxy laminates were tested under Mode I and Mode II conditions, both quasi-statically and in fatigue. Test procedures were adapted from existing standard or pre-standard tests. Samples containing 2% and 4% areal densities of carbon-fibre Z-pins (0.28 mm diameter) were compared with unpinned laminates. Quasi-static tests under displacement control yielded a dramatic increase of the apparent delamination resistance. Specimens with 2% pin density failed in Mode I at loads 170 N, equivalent to an apparent GIC of 2 kJ/m2. Fatigue testing under load control showed that the presence of the through-thickness reinforcement slowed down fatigue delamination propagation.