Localized toughening of carbon/epoxy laminates using dissolvable thermoplastic interleaves and electrospun fibres

Mode-I interlaminar toughness improvement through epoxy-dissolvable thermoplastic phenoxy interleaves of different surface-to-volume ratios is reported. Shear yielding around the crack tip in the reaction-induced phase separated blend morphology was found to be the main toughening mechanism responsible. The dissolution behaviour of thermoplastic phenoxy fibre within epoxy resin was studied, and a simple relationship between dissolution time, temperature, and original fibre diameter is proposed. Thermoplastic interleaves in the form of continuous films and electrospun fibre mats of equivalent weights were employed in order to study the effect of surface-to-volume ratio on dissolution and toughening behaviour. The toughness improvements obtained for the dissolvable thermoplastic nanofibre interleaves were the highest ever reported for these types of toughening concepts, with a dramatic increment from 0.56 kJ/m2 to 1.90 kJ/m2 with only 1.6 wt.% phenoxy interleaves. Differences in toughening behaviour between continuous films and nanofibre mats are explained in relation to differences in dissolution time.