Tensile-shear properties of steel-Al adhesively bonded dissimilar joints and the effect of Al plate thickness

Lap shear dissimilar joints between aluminium (Al) alloy, A6061-T6, and stainless steel, type 304, were fabricated by adhesive bonding. Three Al plates with different thicknesses were used to investigate the effect of the Al plate thickness on the tensile-shear properties, namely the effect of bending stiffness of Al plates. The maximum tensile-shear loads increased with increasing Al plate thicknesses. The fracture through the adhesive layer (cohesive fracture) occurred when the Al plate was the thickest, while the interface fracture between Al plate and adhesive layer appeared on the fracture surface with decreasing Al plate thickness. Fatigue strengths also increased with increasing Al plate thickness. When the fatigue strengths were normalized by the tensile strengths, the effect of the plate thickness became negligible. FEM analyses revealed that the stress concentration at the edge of adhesive on Al side decreased with increasing Al plate thickness, which could be related to the dependence of tensile and fatigue properties on the Al plate thickness.