Damage tolerance of double lap joins under transverse impact

Low velocity impact on adhesive joints represents a worst-case scenario in a bonded structure, so their residual tensile strength is a crucial indicator for damage tolerance of the bonded structures. In this study, narrow double lap joints were tested under two transverse impact energy levels to provide a conservative assessment of damage tolerance. Residual tensile tests were conducted after impact, showing a 49% reduction of pristine joint strength after a 2J impact, and a further reduction (57% of pristine joint strength) post a 3J impact. Residual tensile strength of impacted double lap joints was found to correlate to that of the joints with a similar artificial defect length and location near the inner adherend. The failure mechanisms in the double lap joints were explained via X-ray computed tomography and high-speed photography. 2D FE models were developed using surface interactions based on a virtual crack closure technique in ABAQUS Standard. The FE models capture the residual tensile strength reduction trend, confirming the underlying mixed-mode fracture-controlled failure mode influenced by the asymmetrical damage and loading.