Evolution of macro/mesoscopic thermal-mechanical fields in friction lap joining of surface-textured Al alloy to CFRTP

Controlling interfacial thermal-mechanical condition is key to achieving high-performance joining between carbon fiber reinforced thermoplastic (CFRTP) and metal, especially in friction lap joining (FLJ) processes that enhance mechanical interlocking through preformed micro-textured metal surfaces. In the current work, a novel sequential numerical simulation strategy using Eulerian-based finite element (FE) modeling was developed. This approach aims to deeply investigate the macroscopic thermal-mechanical field evolution and the mesoscopic material flow-filling within localized laser-ablated grooves in FLJ of surface textured Al alloy/carbon fiber reinforced polyamide-66 (PA66). The significance of thermal-mechanical fields in influencing the joint quality was highlighted by quantifying experimentally validated data including peak temperature, high-temperature dwelling time, interface melting depth and deformation depth. As the evaluation index of the interfacial reaction degree, the average reaction time between molten PA66 and metallic surface at each position of the grooves in the whole joining zone was calculated through the obtained simulation results and numeral-form combination strategy. The recommended ranges for peak temperature, average reaction time, and CFRTP thinning ratio to achieve high-performance joints were identified as 320 °C–360 °C, 3.5 s–4.5 s, and <6.5 %, providing new insight and quantitative standard for the performance evaluation of hybrid material joining.