The influence of notching and mixed-adhesives at the bonding area on the strength and stress distribution of dissimilar single-lap joints

Abstract

With the rapid development of new engineering materials, multi-material structures are now widely used to achieve desired performances instead of conventional ones. The increased use of dissimilar adherends such as composites and metals for joining structural parts in aerospace, maritime and civil and transport structures in the past decades make it essential to find methods to improve the performance of this type of joints due to the potential for lightweight products. The first aim of this research is to minimise peak stress concentration by introducing notches in the bonding area to increase the performance of single-lap joints with epoxy adhesive. This is done by utilising the finite element method (FEA) in Abaqus ® software to model a series of single lap joints (SLJ) with various notch designs to find the optimum. Experimental tests are carried out to verify the designs.The optimal design is used then to model various SLJs with mono-adhesive and mixed-adhesives to optimise single-lap joints with dissimilar adherends. The novel geometrical modification reduces peak stresses significantly in the joints with dissimilar adherends, which leads to smaller asymmetric stress distribution along bond-line. The experimental results show significant improvement in the dissimilar joint strength. Compared with using a single material as the adhesive, it is found that using both epoxy and polyurethane as adhesive offers a higher failure load. This can be explained as the polyurethane adhesive provides more uniform stress distribution by transferring stress concentration to the interior part of the overlap length.

A novel dissimilar single-lap joint with interfacial stiffness improvement

“…It can be concluded from the experimental results that the proposed novel design can enhance the strength of the dissimilar SLJ as much as 90.67% (Model-II). This novel design for dissimilar SLJ has superior advantages over available designs in the literature such as notches (38.33% improvement in Ref [30]), spew fillet (36.3% improvement [31]), bi-adhesive (41% and 50% improvement in Ref [30] and [32], respectively) and surface treatment (Improvement of 46.87% in Ref [33], 35% in Ref [34] and 32% in Ref [35]).…”

Load capacity of single-lap adhesive joints made of 2024-T3 aluminium alloy sheets after shot peening

“…The stresses in the near-edge zone can also be reduced by changing the geometry of the laps. These changes may include, for example, rounding adherend corners [16][17][18], tapering [16,19,20] and notching the adherends [21,22]. Changing the adherends' geometry allows the peel stresses concentrated at the ends of the overlap to be reduced and, as a result, increases joint strength.…”

The Use of Neural Networks in the Analysis of Dual Adhesive Single Lap Joints Subjected to Uniaxial Tensile Test

“…In order to further optimize a mixed-adhesive connection and the separation of both adhesive layers, notches in the joined sheets can be used, an approach that was presented in [ 12 ]. Five types of connections were analyzed: a control without notches and test pieces with two, three, four and five notches.…”