High-speed joining of hybrid metal-polymer joints during the friction-assisted joining process

The influence of joining time during the friction-assisted joining process was investigated. Experimental tests were conducted on aluminum AA7075 and polyamide PA66. An instrumented equipment was adopted to measure the processing forces and infrared thermography was involved to measure the temperature at the upper metal surface. A numerical model was developed to determine the temperature at hidden regions (the tool-metal and the metal-polymer interfaces). Mechanical characterization tests were performed to establish the influence of the joining time under different process parameter combinations on the mechanical behavior of the joints. The results indicated that high plunging rates (1000 N/s) provided almost double heating rates (over 200 °C/s), and higher energy efficiency as compared to lower plunging rates (100 N/s). High-speed joining involved several advantages: it hindered the formation and coalescence of porosities and it enabled the localization of the heated region to a thin layer of polymer. High-speed joining also led to reduced polymer overflow even at high temperatures. The joints made under high-speed conditions showed higher strength than those produced under low-speed joining conditions.