Impact of Adhesively Bonded Composite Joints with Edge Effect

A pilot project has been carried out to investigate the effect of impact on single-lap bonded composite joints based on AS4-8552 laminates and Cybond BR4535A adhesive. Low velocity impacts at an energy level sufficient to cause barely visible impact damage, were conducted on single lap joint specimens at different joint positions. Impact caused delaminations in the upper and lower laminates and localised through-thickness cracking in the adhesive. Residual tensile joint strengths of the impacted joint specimens with near-edge damage were reduced to approximately 50% of the un-impacted value. Failure surface inspections revealed localised through-thickness adhesive shear cracking as a governor of the original impact delamination pattern in the laminates and laminate delamination as the cause of ultimate tensile failure.