Multiaxial stress effects on bonding strength in adhesively bonded joints

This study investigates adhesive bonding as a crucial engineering technique for joining materials, with a focus on load distribution, structural enhancement, and weight reduction. Advances in adhesive formulations, surface preparation, and application techniques continue to expand its capabilities. The research addresses stresses in hybrid joints resulting from pre-tensioning bolts and subsequent axial loading, emphasizing the influence of normal stresses on the critical adhesive-steel interface. Off-axis samples are bonded to mild steel using four different adhesives: SW7240, S370, DP460 (2K-epoxies), and SF479 (2K polyurethane). The choice of adhesive significantly influences shear strength under various loading conditions. Formulating this interaction in terms of maximum shear or von Mises stresses leads to relatively complex failure criteria that make the further analysis dependent on each adhesive. On the other hand, expressing strength at maximum principal stress significantly simplifies comparative analysis, as it consistently exhibits an almost linear trend, indicating strength reduction with increasing hydrostatic pressure for all adhesives, potentially simplifying subsequent strength predictions of hybrid joints.