Mechanical Properties of CFRP/2024 Al Alloy Joints Fabricated by Transverse Ultrasonic-Vibration-Assisted Riveting

The mechanical performance of CFRP/2024 Al alloy hybrid laminates joined by transverse ultrasonic vibration-assisted riveting (TUVAR) was investigated. The experiments were conducted on a self-developed ultrasonic riveting system with a power of 3000 W and a vibration frequency of 19.8 kHz, covering ultrasonic amplitudes from 0 to 24 μm. Test specimens were fabricated from T300/CFRP laminates, 2024 Al alloy sheets, and 2A10 Al alloy rivets. The influences of ultrasonic amplitudes (12 μm, 16 μm, 20 μm, and 24 μm) on riveting load, driven head geometry, interference, static tensile strength, and cyclic loading behavior were systematically analyzed. The results showed that TUVAR reduced the riveting force and promoted rivet deformation. As the amplitude increased, the driven head diameter increased, and the driven head height decreased, with a maximum reduction of 6.62%. The mean interference generally increased up to 20 μm and then decreased slightly at 24 μm; the relative interference variance coefficient ranged from 0.070 to 0.155 under TUVAR. Static tensile tests showed that the joint strength first increased and then decreased with increasing amplitude, with the highest mean static tensile load obtained at 20 μm. Cyclic tensile tests indicated that load-bearing capacity was improved with increasing amplitude, while the maximum deviation was maintained within 3.5%. These findings demonstrate that TUVAR can enhance both the forming quality and the mechanical performance of CFRP/2024 Al alloy riveted joints, and provide a useful reference for the high-performance joining of composite-metal hybrid structures in aerospace applications.