Effect of residual epoxy on single lap joints performance

Abstract

Design for remanufacturing of adhesively bonded composite structure emphasizes the product features such as ease of disassembly, surface reconditioning, reassembly and validating the structural integrity of rebonded joints. After disassembly of bonded joints, the adhesive on the adherend surfaces should be removed for reassembly. Some part of adhesives will be left over in complex, undulated bonding surface and this residual adhesive may affect the reassembled joint mechanical performance. In this experimental work, two different adherends namely aluminium (Al) and glass fibre reinforced polymer (GFRP) were bonded with 3M DP490 epoxy adhesive and the joint shear strength was determined by tensile single lap shear testing. Further, joints with induced residual epoxy were fabricated and the effect of different percentage of residual epoxy on joint shear strength was investigated. The test result shows that there was no significant reduction in lap shear strength of both GFRP and Al alloy joints. There was no evidence of failure at the residual-fresh epoxy interface that shows good mechanical compatibility between the residual and fresh epoxy. Furthermore, the surface profile measurements of materials surfaces were studied and the residual epoxy surface texture ensures proper mechanical anchoring with fresh epoxy.