Failure analysis of CFRP-aluminum electromagnetic self-pierce riveting-bonded joints subjected to highspeed loading

Abstract

The mechanical performance of dissimilar material riveted joints is important for passenger safety during a crash situation. Hence, in this paper, the mechanical properties of CFRP-aluminum electromagnetic self-pierce riveting-bonded (E-SPR-bonded) joints under quasi-static and dynamic loading was investigated. First, the hybrid joints were manufactured under five discharge energies to explore the best process parameter, then, the effect of shearing speed on the mechanical properties were studied. Digital image correlation (DIC) method was carried out to further understand the surface strain distribution. Results indicated that the evolution of shear tests could be divided into two stages, including two peak loads, named peak A and peak B, respectively. The hybrid joint at 7.7 kJ had the best peak load during static load. Under the dynamic loading condition, the peak load increased with ascending load speed, especially the peak B, under 4, 8 and 12 m/s, were 189.0 %, 205.5 %, and 215 % higher than that of 2 mm/min, respectively. The hardening effect of sheets was increased under high shear speeds, which dominated the fracture behaviors of the bonding layer. The hybrid joints failure behavior was the CFRP fracture, and the rivet remained in the aluminum sheets. The results could provide theoretical guidance for the structural design of automobiles and promote its engineering application.