Critical Influence of Rivet Head Height on Corrosion Performance of CFRP/Aluminum Self-Piercing Riveted Joints

Abstract

This study investigates how rivet head height affects the corrosion performance of carbon fiber reinforcedplastic (CFRP) to aluminum alloy self-piercing riveted joints. Specimens with two different head heightswere prepared. A rivet head protruding out of the top CFRP laminate forms the proud head height whilea rivet head penetrating into the top CFRP generates the flush head height. The salt spray test evaluatedcorrosion performance. The flush head joints suffered from severe corrosion on the rivet head. Thus, thetensile shear load of flush head joints was substantially reduced. Electrochemical corrosion tests investigatedthe corrosion mechanisms. The deeper indentation of the flush head height damaged the CFRP around therivet head. The exposure of damaged fibers from the matrix increased the cathodic potential of local CFRP. The increased potential of damaged CFRP accelerated the galvanic corrosion of the rivet head. After therivet head coating material corroded, a strong galvanic couple was formed between the rivet head basemetal (boron steel) and the damaged CFRP, further accelerating the flush rivet head corrosion. The resultsof this study suggest that rivet head flushness should be avoided to enhance the corrosion performanceof CFRP to aluminum alloy self-piercing riveted joints.