Forming law and mechanical property of carbon fibre reinforced plastics and aluminum alloy self-piercing riveted joint

There are great potential and application space of carbon fibre reinforced plastics (CFRP) in lightweight vehicle body manufacturing, and realizing effective connection of the material is still a great challenge. The connection process between CFRP and aluminum alloy plate was explored using self-piercing riveting (SPR) technology, and the effects of rivet type, punching speed and riveting die dimension on joint structural parameters were summarized, then the forming mechanism of undercut structure in the riveting process was analyzed, the strength performance and failure mode of joints with various plate thicknesses were also investigated. It is found that the undercut value of SPR joint is affected by both the penetration depth of the rivet shank into the lower plate and the local moment on the rivet toe, and increases with the rise of the effective rivet length, the punching speed and the depth of the die. Through process optimization, SPR joints between CFRP and aluminum plates with good forming structure can be obtained, and the mechanical internal locking strength can reach 89% of that of aluminum alloy plates joint. However, compared with aluminum alloy joint with the same plate thickness, the outstanding weakness of CFRP joint is the ability of its CFRP upper plate to resist concentrated stress damage.