Necessity and usefulness of analyzing 3D corner singularity index and 3D corner ISSF to evaluate adhesive strength

In this paper, necessity and usefulness of analyzing intensity of singular stress filed (ISSF) at 3D interface corner are discussed to evaluate adhesive strength of scarf joint. Previous studies showed that the adhesive strength of scarf joints can be expressed as a constant critical 2D ISSF at the interface edge when a tensile singular stress appears. In this paper, first, the special bad pair condition when a compressive singular stress occurs at the 2D interface edge in the scarf joint is described in terms of the scarf angle and the material combination of the adherend and the adhesive. Second, under this special condition, the detail analysis method is described for the 3D corner singularity index and the 3D corner ISSF. Third, under this special condition, the adhesive strength of the scarf joint is newly investigated in terms of the 3D corner ISSF. It is found that the adhesive failure criterion can be expressed as a constant critical intensity of singular stress field at the interface corner. This new finding shows that the 3D corner ISSF is especially useful for evaluating the adhesive strength of the scarf joints which have the compressive singular stress at the interface edge.