Ultrasonic welding with surface engineering for Al6061/CF-PPS hybrid joint processing

Lightweight hybrid joints are essential for advanced automotive and aerospace structures; yet, the integration of dissimilar materials, such as aluminum alloys and carbon-fiber reinforced thermoplastics, presents significant challenges. This work examines developments in ultrasonic welding of Al6061 and carbon fiber-reinforced polyphenylene sulfide (CF-PPS), utilizing tailored surface changes on the aluminum substrate to improve interfacial bonding. Drilled surface patterns were implemented to enhance mechanical interlocking and optimize energy distribution during welding. A Rinco 3000 ultrasonic welding system (20 kHz, 3 kW) was utilized. Process variables like amplitude = 20 kHz, horn pressure = 0.8 MPa, weld time = 2.5 sec, and hold time of 3 sec were inputs throughout the experiment. The optimized drilled pattern (P3) attained a maximal lap-shear strength of 24.2 MPa, representing a 34.3% enhancement over a flat interface and exhibiting 30–50% higher performance compared to previously reported adhesive and friction stir welded. Supporting investigations validated the processing technique by confirming the densification of CF-PPS in grooves, better crystallinity, and enhanced interfacial bonding. Failure surface examination indicated predominant cohesive fracture within the polymer, with minimal interfacial separation, thereby confirming robust metallurgical-mechanical bonding. In comparison to traditional joining methods, ultrasonic welding exhibited accelerated cycle times, the removal of consumables, and enhanced scalability for industrial manufacturing. The findings confirm that ultrasonic welding with tailored surface alterations is an effective processing technique for producing lightweight, durable Al/CF-PPS hybrid joints.