Effect of elevated test temperature on the tensile strength and failure mechanism of hot-pressed dissimilar joints of laser ablation-treated AA5754-H111 and thermoplastic composite

Abstract Evaluation of directly bonded single-lap joint (SLJ) obtained using Al5754 alloy and 20 wt% long glass fiber-reinforced polypropylene (PP) is performed via the lap-shear testing at various temperatures. A fiber laser is used to form a multi-groove microstructure on the aluminum (Al) surface. The bonding regions are investigated microscopically before and after the mechanical testing. Dissimilar joint is manufactured under a 100 kN force at 200 °C for 60 min through hot-pressing technique without using any adhesives. Afterward, lap-shear strength of the joints is determined under elevated working temperatures (25, 75 and 125 °C). Damaged surfaces are also scrutinized for studying the failure mechanism of the joints. According to the experimental results, mechanical anchoring between the Al alloy substrate and thermoplastic composite (TPC) is formed at the interface through the applied laser treatment. Strength exhibits a significant decrease with the test temperature increasing from 25 to 125 °C. Fiber/matrix debonding is the dominant failure mode in the composite adherend. The SEM observations also highlight the pulled-out fibers in the PP composite at the elevated temperatures.