Study on Tensile Shear Strength of Dissimilar Lap Joints for Multi-Material Structures

In order to design a future multi-material car body, both an appropriate selection of the advanced materials and a suitable assignment of joining methods are essential technologies, where the data-base of the advanced multi-material joint performance has to be prepared. In this research various advanced multi-material dissimilar lap joints were fabricated and the tensile shear strength of those joints was evaluated. The materials used were an ultra-high strength steel (UHHS), a carbon fiber reinforced thermo-plastic (CFRTP) and an aluminum alloy of A5083P-O. The resistance spot welding (RSW) and refill friction stir spot welding (RFSSW) were employed for joining UHHS and A5083P-O, while UHHS & CFRTP and A5083P-O & CFRTP lap joints were fabricated by the friction stir spot welding (FSSW) and laser irradiation assistance plastic welding (LIAPW). The tensile shear strength of UHHS & A5083P-O joint joined by RFSSW was found to be 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 was larger than that of FSSW. Moreover, all the tensile shear tests suggest that the total heat input during joining process might not influence the tensile shear strength proportionally and the relationship between the joining conditions and tensile shear strength has be evaluated by using the artificial intelligence technologies in order to contribute the data-base of the advanced multi-material joint performance.