MIXED-MODE FRACTURE OF A LUBRICATED INTERFACE

The fracture of an interface containing a liquid was investigated under nominally mixed-mode conditions. The experiments were designed to be a study of a model interface for which frictional effects are minimised. Alternatively, the system could be considered to provide an analogy for an interface along which there is little resistance to shear. The fracture resistance was found to be independent of the nominal phase angle, and it was in excellent agreement with the interfacial surface energy determined by a capillary-rise experiment. Furthermore, the study emphasised the importance of the difference between a nominal phase angle determined from macroscopic considerations and the local phase angle appropriate for the crack-tip region,