Flexural properties and failure mechanisms of infusible thermoplastic-and thermosetting based composite materials for marine applications

This study aims to evaluate the flexural properties and associated failure mechanisms of a reactive thermoplastic relative to traditional thermosetting resin systems (polyester, vinylester, epoxy) for potential application in marine vessels over 50 m in length, as part of the H2020 FIBRESHIP project. All resin systems are compatible with the vacuum assisted liquid resin infusion manufacturing technique commonly used in small/medium size shipyards. Glass fibre reinforced polymer (GFRP) laminates were manufactured, test samples extracted, immersed in deionised water or an organic liquid (diesel) and mechanically tested to evaluate the flexural strength and modulus. Failure mechanisms are analysed by scanning electron microscope (SEM). In terms of flexural strength, the reactive thermoplastic based laminate performed similar to the epoxy in terms of retained strength in both deionised water and diesel. The governing failure mode of fibre buckling and kink band formation coupled with interlaminar cracking was identified for both the epoxy and the thermoplastic. The vinylester laminate retained equivalent strength in all three environments while polyester showed the greatest reduction in water due to extensive interlaminar cracking. Overall, the flexural properties of the reactive thermoplastic are shown to be competitive with traditional candidate resin systems for marine structures. The strength reduction and failure modes in the dry, wet and diesel condition were similar to the epoxy while the reduction of modulus was negligible in water and less than 10% in diesel.