Evaluation on Joint Performances of Advanced Multi-Material Dissimilar Lap Joints

Abstract

As a result of R&D efforts about the advanced materials, an ultra-high strength steel (UHHS) and a carbon fiber reinforced thermos-plastic (CFRTP) have been developed. In this study, various advanced multi-material dissimilar lap joints using UHHS, CFRTP and an aluminum alloy of A5083P-O were fabricated by the resistance spot welding (RSW), refill friction stir spot welding (RFSSW), friction stir spot welding (FSSW) and laser irradiation assistance plastic welding (LIAPW). Where, the total heat input for each joining method was varied in order to examine the influence of welding condition on joint performances, which were the tensile shear strength, shear fatigue property and corrosion shear fatigue property. The tensile shear strength of UHHS and A5083P-O joined by RFSSW is almost two times of that produced by RSW, and this difference seems to be mainly caused by the difference of joint area. The difference of joint area also affects the tensile shear strength of UHHS & CFRTP or A5083P-O &CFRTP lap joints made by FSSW and LIAPW, and the joint strength of LIAPW is larger than that of FSSW. As for the shear fatigue tests, it is found that the fatigue strength seems to decrease almost monotonically with increasing the applied load regardless of the types of dissimilar materials. Moreover, through the corrosion shear fatigue tests for A5083P-O and CFRTP joined by FSSW or LIAPW, it is found that the corrosion fatigue property seems to be controlled by the crack propagation behavior.