Shear stress distribution in adhesive layers of a double-lap joint with void or bond separation

In this work, stress distribution in adhesive layers of a double-lap joint subjected to tension and suffering from a void or a partial debond at the adhesiveadherend interface is examined. For symmetric voids, the deduced equilibrium equations are decoupled for better application of boundary conditions at the extreme ends of each adhesive layer. The proposed method of solution has resulted in better estimates on peak shear stress developed in the adhesive layers. The results based on analytical solution are compared with those of finite element findings. Very good agreement is observed between the two. The major difference between stresses stemming from debonds and voids occurs at the edge of the large size defects. For small central defects, it is hardly discernible by the stresses to distinguish the type of defect. Moreover, there appears to be an optimum length to thickness ratio for each adhesive layer which produces minimum peak interfacial shear stress. This value seems to be a function of defect size and location. A double-lap joint shows to experience smaller interfacial shear stresses due to a single void or debond in comparison with a single-lap joint with a similar defect. The peak interfacial shear stress in a double-lap joint suffering from symmetric voids or debonds is still lower than that of a single-lap joint with a single defect of the same size and location.