Characterisation of a glass-fibre reinforced vinylester to steel joint for use between a naval GRP superstructure and a steel hull

The use of polymer composites in naval applications is becoming more common, particularly due to the potential weight savings. The mechanical response of a prototype joint between a glass-fibre reinforced polymer superstructure and a steel hull formed via a resin infusion process was examined and subsequently modified to improve performance through a combined programme of modelling and mechanical testing. The GRP–steel interface was shown to be critical to the mechanical performance of the joint. The effects of post-cure temperature and surface preparation on the GRP–steel interface were evaluated through the use of the four-point bend delamination test. The results show interfacial toughness to increase greatly with surface roughness for low surface roughness up to a particular roughness above which no further increase is obtained. A similar increase is observed for low temperature post-cure but for higher temperatures a significant decrease is observed.