On the design of debond-resistant bimaterials: Part II: A comparison of free-edge and interface crack approaches

Abstract

In Part I of this paper, the authors have adopted a fracture mechanics-type approach to characterize the intensity of the free-edge stress singularity governing initiation of debonding for the general plane elasticity problem of a bimaterial strip under uniform edge loadings. In this study, the same global problem configuration is used to provide an extensive comparison between the free-edge singularity and interface crack approaches to bimaterial design. While similar trends in the intensities of the free-edge and interface crack singularities are shown to be largely governed by trends in the global interface stress resultants, fundamental differences in the local singular fields are shown in some cases to result in competing design implications. As a result, design guidelines are provided with respect to both free-edge debonding and steady-state interface crack extension over a wide range of practical material properties and relative layer thicknesses. Finally, the methods discussed herein are applied to a four-layer bimaterial configuration, for which the three interfaces are compared with respect to both free-edge debonding and subsequent interface crack extension over a wide range of elastic mismatches.