Effects of repeated laser texturing scans on mechanical properties and microstructure of CFRTP/Al alloy ultrasonic welded joints

This paper investigated ultrasonic welding of dissimilar joints of carbon fiber-reinforced thermoplastic (CFRTP) with resin matrix and aluminum alloy, pioneering the application of laser texturing on CFRTP surfaces to reveal its impact on the mechanical properties of the welded joints. The performed macro- and microstructural analyses of the joint sections made it possible to specify the interface bonding characteristics and relevant mechanisms. The results showed that with the increased depth-to-width ratio of laser texturing, the joint area of the intermediate transition layer on the CFRTP surface changed from continuous filling to discontinuous one, while the joint’s tensile shear strength first grew and then dropped. At a 2.36 depth-to-width ratio, the ultrasonic welding lap joint of CFRTP-Al alloy with the best forming and mechanical properties was obtained, with the joint’s cohesive shear force reaching 3862 N. The interface bonding mechanism was mechanical interlocking, and the joint’s fractures modes were mainly cohesive or mixed (adhesive + cohesive).