Marine environmental effects on a graphene reinforced epoxy adhered single lap joint between metals and CFRP

This study investigates the marine environmental effects on the bonding strength of graphene nanoplatelets (GNPs) reinforced adhesive for a metal/composite single lap joint. Samples were immersed for periods of 1, 2 and 3 weeks in a 50 °C, 3.5% NaCl solution, with the purpose of the heat being the creation of an environment in which simulated an increased ageing period in the joint structure. In a dry condition, the use of GNPs produced a slight increase in lap shear strength of 17% and 14% in the carbon fibre reinforced plastics (CFRP) composite laminate to aluminium and stainless-steel joints respectively. Post immersion, the stainless-steel samples endured 10% less strength degradation than the aluminium samples in the cases with and without GNPs, however the degradation between the same materials with and without GNPs differed less than 2%. On the other hand, the rate at which the materials with GNPs and without GNPs degraded, differed greatly between immersion periods. Mathematical methods were carried out via analytical calculation and FEA modelling, for which values converged with experimental results. The outcomes of these experiments have been the production of highly useful information in terms of material selection and adhesive modification via GNPs for use in the marine environment.