Effect of curing time on phase morphology and fracture toughness of PEK-C film interleaved carbon fibre/epoxy composite laminates

Abstract

The phase morphology developed by thermosetting and thermoplastic resin is one of the main concerns in interleaved thermosetting composites by thermoplastic resin, which directly affects the toughening efficiency. The carbon fibre reinforced epoxy matrix composite laminates were interleaved by Polyetherketone-cardo (PEK-C) films and the effect of curing time on the phase morphology spectrum and fracture toughness was investigated in the study. The microstructure-property correlation was explored. The results showed that the PEK-C film interlayer was efficient in the interlaminar toughening and the fracture toughness (GIC) was enhanced by 90.65% at curing time of 1 h. Nevertheless, increasing curing time weakened toughening effect of PEK-C films and GIC was only increased by 9.37% under the curing time of 3 h. The characteristic morphology spectrum in the interlaminar region, consisting of homogeneous PEK-C resin, nodular dualphase and sea-island dualphase, contributed to the improvement of toughness. The homogeneous PEK-C layer was decreased with the curing time increasing due to the more fully permeation of epoxy, resulting in the crack path change from the center of interlaminar region and the interface between interlaminar region and composite layer to merely the interface, which might be the main reason for the weakening of measured crack propagation resistance.