Bio-inspired helicoidal thin-ply carbon fiber reinforced epoxy laminates with nylon microparticles for improved toughness and healing

The addition of thermoplastic particulates to carbon fiber reinforced epoxy to concurrently improve toughness and aid in repairs is reported. Bio-inspired helicoidal laminates and conventional quasi-isotropic laminates embedded with 3 wt% Nylon6 interlaminar toughening/healing agent were fabricated and subjected to drop impacts. Subsequently, the damaged laminates were healed, and their out-of-plane performance was compared to undamaged virgin laminates. Under impact, larger matrix damage is formed in the helicoidal laminates while fiber damage, which cannot be repaired effectively, is suppressed. The helicoidal laminate not only fully recovers its out-of-plane peak load from a significantly higher impact energy than the conventional laminate, the peak load of the healed helicoidal laminate even surpasses its virgin counterpart by up to 26%. However, load recovery rate of helicoidal laminates is significantly dependant on their inter-ply angle: whilst helicoidal laminates with 6° inter-ply angle fully recover from 43.4 J impact, helicoidal laminates with 18° inter-ply angle only fully recover from 24.8 J impact.