Graphene nanoplatelets/epoxy nanocomposites as conductive adhesives for out-of-autoclave in-situ CFRPs repair

Novel out-of-autoclave (OoA) strategies for repairing carbon fibre reinforced plastics (CFRPs) were investigated to enable facile maintenance of components and, thus, reduce unnecessary scrappage. Oven cured GNPs/epoxy bulk and film nanocomposites were first fabricated over a range of GNPs loadings to determine their percolation threshold and Joule heating properties. Based upon these results, electrically conductive uncured nanocomposites with different GNPs loadings were then used as adhesives to repair CFRPs through Joule heat curing of the electrically conductive GNPs network embedded in the epoxy. The GNPs loading in the adhesive was found not to influence the spatial distribution of the heat generated during repair, however it did affect the heating rate. The lap shear strengths found for the CFRPs repaired by Joule heating were the same as though for CFRPs repaired using a conventional oven curing method, evidencing the effectiveness of this approach as an OoA repair method. Scanning electron microscopy revealed the coexistence of interfacial and cohesive failure mechanisms, with an increasing dominance of the cohesive as the GNPs loading increased.