Inhibiting delaminations in fibre reinforced plastic laminates with dropped plies

Cut plies were incorporated at the centre of unidirectional glass fibre laminates to simulate the loading conditions observed around dropped plies in tapered structures. Specimens were tested aggressively in tensile fatigue in order to initiate delamination at the ply cuts and propagate this along the interfaces between the continuous outer plies and discontinuous (cut) inner plies. Narrow strips of thermoplastic film were interleaved at specific locations along the delaminating interfaces to investigate their ability to slow or inhibit the delamination growth. Polyimide and EMAA thermoplastic films were investigated: whilst the polyimide film appeared to have minimal effect, the EMAA film proved highly successful in preventing delamination growth under the fatigue conditions.