Abstract: Mixed-modulus single-lap joints are the bonded joints in which all of the load between two adherends is transferred within the variable modulus adhesive layer in the overlap region. The technique is demonstrated to combine the advantages of the continuous connection and of lowering the stress concentrations due to the variation of adhesive properties, which implies that a huge potential of bonded adherends such as composite materials and a substantial increase in joint strength could be realized. The theoretical stress model for symmetric bi-adhesive single-lap joints made of isotropic adherends is proposed on the basis of the linear elasticity mono-adhesive theory. The bending effect caused by the non-axial loading of the adherends and the adhesive peel stress, which is generally considered to be critical to joint failure, are taken into account in this investigation. The adhesive shear and peel stresses and upper adherend’s longitudinal normal stress in the analytical solution are obtained and compared with the numerical solutions determined by the two-dimensional linear elastic finite element analysis (FEA). The numerical experiment shows that the results of the theoretical and FEA models agree well. Finally, the relevant key parameters for the adhesive peak shear and peel stresses are identified and discussed.

Key words: Adhesive bonded, Bending effect, Mixed-modulus bonding, Parametric study, Single-lap joint, Stress analysis