Adhesively Bonded Composite Patch Repair in Load-Bearing Applications for the Aviation Industry: Manufacturing, Design, and Simulation

Four adhesively bonded composite patch repairs are considered: with one and two double CFRP layers and with scarf ratios of 1:15 and 1:30. Prepregs are applied to an artificially cracked aluminum plate and bonded using a film adhesive. Considering curing-induced deflection of patches, samples with two double CFRP layers and a scarf ratio of 1:15 exhibit the highest deflection, while the patch with one double CFRP layer and a scarf ratio of 1:30 shows the lowest deflection. FE simulations align with experimental results showing deviations between -3% and +16%. Fatigue results of crack length as function of cycles reveal that patched samples have longer lifetimes (3.2-4.3 times) compared to nonpatched samples. Among patched samples, those with two double CFRP layers and a scarf ratio of 1:15 provide approximately 20% and 8% longer service life compared to counterparts with one double CFRP layer and a scarf ratio of 1:30, respectively.