Optimizing joint structure and performance in friction spot joining of aluminum alloy AA6061 and poly-ether-ether-ketone (PEEK)

This study investigated the challenge of joining poly-ether-ether-ketone (PEEK) to aluminum alloy AA6061 through friction spot joining (FSpJ), by examining the impact of surface treatment of AA6061 sheets and analyzing various process parameters' effects on joint interface morphology, tensile-shear strength, and failure. Results indicated a peak interface temperature may reach 400 degrees C during FSpJ, with a 0.5-0.9 mm molten PEEK layer containing sealed bubbles. Notably, Boehmite treatment significantly improved joint strength, although the primary failure occurred in the PEEK base material. An optimization through response surface method (RSM) analysis identified plunging depth as the most influential factor in joint strength, and a peak load of 4576 N with an optimized combination of pin rotation speed, plunging depth, and dwell time was achieved. Using optimized process parameters, strong PEEK-AA6061 joints can be formed, and the approach is extendable to joining other metallic and polymeric materials.