Since cracks often initiates at the interface and propagate along the interface for materials with dissimilar interfaces such as metal/metal and polymer/metal, such as thermal sprayed materials, coated steel sheets and semiconductor packages, evaluation of interfacial strengths are an important issue for the reliability of these materials. However, it is difficult to evaluate the interfacial strength of such materials when they are subjected to the same tensile tests as homogeneous materials, because in many cases a mixture of interfacial and base material fracture occurs. Currently, the most common methods for evaluating the interfacial strength of these materials are to conduct strength tests by introducing a pre-crack at the interface or to test for crack propagation from the interfacial edge, wherein the interfacial strengths have been evaluated by parameters that define the stress singular fields at the interfacial crack or the dissimilar edge. We overviewed methods for evaluating the strengths of the dissimilar interfaces based on these stress singularity parameters.
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