Residual stress profiles in coated riveted joints of dissimilar materials using SPR joining technique

The United Kingdom has set a formidable net-zero target of 100% emission reduction by 2050, emphasising the urgent need for progress in sustainability efforts. Given the significant role of the automotive industry in CO2 emissions, there is a growing demand for lightweight multi-material structures to mitigate environmental impact. Carbon fibre reinforced polymer (CFRP) and Aluminium (Al) have emerged as pivotal materials due to their superior strength-to-weight ratio, particularly in the context of vehicle electrification. However, understanding and mitigating joint failure resulting from residual stresses in the Self-piercing riveting (SPR) process remains a critical area of investigation. Prior studies have successfully quantified residual stresses in SPR joints, primarily focusing on similar metallic materials. This current research extends the inquiry to encompass both dissimilar materials i.e. CFRP-Al with carbon steel rivet joint, with a particular emphasis on the resistance encountered during rivet insertion, potentially leading to stress-induced failures. Employing various coated rivets (carbon and Aluminium-based) with distinctive characteristics, this study aims to unravel the intricate interplay between surface properties, coating hardness, and residual stress formation during SPR joining, ultimately enhancing our comprehension of these critical structural elements.