Fatigue performance of electromagnetic self-pierce riveting-bonding hybrid joint under alternating load and corrosion coupling conditions

Electromagnetic self-pierce riveting (E-SPR) process was suitable for joining carbon fiber reinforced plastics (CFRP) and aluminum sheets. The E-SPR joints of dissimilar material still suffered from corrosion, and bonding could be an auxiliary process to improve corrosion resistance of joints. This paper investigated the fatigue characteristics of electromagnetic self-pierce riveting-bonding hybrid joints under alternating load and corrosion coupling conditions. Neutral salt spray (NSS) test, microscope observation, and fatigue test were conducted. Results showed that the adhesives not only improved the joint's corrosion resistance, but also its mechanical properties. Specifically, the shear curves contained two peak loads, namely peak A and peak B. Corrosion was the greatest at 840 h, where peak A was 42.86% less than at 0 h, but peak B had little effect. Moreover, the addition of adhesives significantly impacted the fatigue characteristics of the joints after corrosion. The E-SPR-bonded joints still appeared good anti-fatigue characteristics within 168 h of corrosion. The fatigue failure modes were fractures in the CFRP sheets and the rivets remaining in the aluminum sheets. The influence mechanism of corrosion on fatigue was revealed. The water molecule and chloride ions penetrated the adhesives to cause hydrolysis, increased the plasticity of the adhesives and decreased the bond strength, which reduced the fatigue characteristics. The results provided theoretical guidance for E-SPR-bonded joints applied in engineering applications.