A numerical study on stress mitigation in through-thickness tailored bi-adhesive single-lap joints

Abstract

In bi-adhesive single-lap joints (SLJs), longitudinal grading of adhesive compliance leads to peak stress concentration to the bi-adhesive interface (due to mismatch in properties). Due to this additional stress concentration at the bi-adhesive interface, the failure initiation threshold is lowered. In this paper, the stress distribution in the compliance-tailored bi-adhesive joints is investigated numerically. Peak stress at the bi-adhesive interface is diffused by geometrically grading the bi-adhesive interface in the longitudinal and transverse (through the thickness) directions. Linear and non-linear (material and geometric) finite element (FE) analyses were performed for two different set of bi-adhesive bondlines and joint configurations. FE results were benchmarked with published experimental and numerical data. Peak peel stress and peak shear stress are decreased by 29–70% and 8%, respectively, when the bi-adhesive interface is graded geometrically in the transverse and longitudinal directions as opposed to longitudinal tailoring alone. Moreover, the bi-adhesive interface’s stress concentration is reduced significantly. This leads to a more homogeneous stress distribution throughout the bond-layer. A thorough investigation reveals that through-thickness compliance tailoring of the bi-adhesive in SLJ can be used to increase tolerance to high load levels, achieve uniform stress distribution along the bond-layer, and reach the optimum joint stiffness.HighlightsA new approach for stress mitigation involving through the thickness tailoring of adhesive is introducedProposed approach is validated for two sets of bi-adhesive systems and two joint configurationsFinite element results are validated with published experimental dataLoad carrying capacity of joints is enhanced by diffusing peak stresses away from the bi-adhesive interface