Experimental and numerical investigation of the interfacial strength of bi-material joints

An integrated experimental and numerical investigation is employed to examine the interfacial strength of bi-material bonded joints with the aim to quantify the influence of three-dimensional (3-D) stress singularity. The stress singularities at 3-D interface corners and edges have been investigated numerically using finite element methods (FEM). It is found that the effect of the vertex angle on the order of stress singularity at interface corner can be eliminated by smoothing the intersection of interface edges, which can be achieved simply by generating a circular-arc fillet at the intersection of the two free side surfaces. Motivated by this, four-point flexure experiments of bi-material bonded joints, both with and without circular-arc fillet, are conducted. The experimental results suggested that, with a circular-arc fillet design, the strength of the joints may be increased due to the disappearance of 3-D stress singularity at interface corner. Finally, based on an analysis of the intensity of the singularity, an empirical equation that describes the relationship between the failure stress and the largest value of tress singularity order −λ at 3-D interface was determined to predict the interfacial strength of brittle bonded joints.