Impact response of interphase-modified CFRP laminates: an assessment across PEI, PES, PSU, and PC

This study evaluates the low-velocity impact response of aerospace-grade epoxy laminates (M18/1) interleaved with four distinct thermoplastic films (PEI, PES, PSU, PC). Impact performance was correlated with quasi-static fracture toughness to assess the transferability of intrinsic polymer properties to dynamic loading. The results reveal a fundamental trade-off governed by chemical compatibility. Chemically compatible interphases (PEI, PES) successfully bridged the stiffness mismatch, increasing the damage initiation threshold by up to 23%, although total energy absorption plateaued due to matrix saturation. Conversely, the incompatible Polycarbonate (PC) system exhibited a mechanism shift: despite high intrinsic ductility, low Mode I adhesion (GIc) caused immediate decoupling, triggering a pseudoplastic sliding mode that increased energy absorption (+10%) at the cost of structural integrity. Polysulfone (PSU) revealed an inefficient compromise, suffering from premature adhesive failure without providing significant energy dissipation. These findings challenge established propagation-based models, identifying Mode I initiation toughness as the critical ‘gatekeeper’ for structural toughening in hybrid laminates.