Interlaminar toughening of woven fabric carbon/epoxy composite laminates using hybrid aramid/phenoxy interleaves

The influence of a hybrid interleaf system based on aramid and phenoxy fibres on the interlaminar toughness and damage tolerance of epoxy based carbon fibre reinforced plastic (CFRP) laminates was studied. An interleaf consisting of a non-woven aramid mat was either used on its own or in combination with epoxy-dissolvable thermoplastic phenoxy fibres. These thermoplastic phenoxy fibres are miscible with the epoxy resin and phase separate upon curing to improve ductility and toughness. Tensile properties, Mode-I fracture toughness, interlaminar shear strength (ILSS), as well as compression after impact (CAI) properties of the toughened CFRP laminates have all been characterized and analysed. Fractography was used to identify the toughening mechanisms in the CFRP laminates with different interleaf compositions. At the optimal interleaf composition, obvious synergic effects were found in terms of the overall mechanical performance of these hybrid composite laminates, including a near 150% increment in interlaminar fracture toughness in comparison to a reference CFRP laminate.