Mechanical Sciences: Mixed Mode Fracture at Bimaterial Interfaces

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The objective of this research project is to develop the experimental tools for a direct evaluation of the fracture processes that occur in the separation of dissimilar materials along their interface, with a view to understanding the delamination phenomenon of layered solids. In particular, local fracture mode interactions and the viscoelastic nature of the adhesive or matrix materials will be examined for their influence on the propagation rates of cracks that are constrained to grow along the interface between dissimilar materials. Interpretation of thefracture processes will be based on direct observation and measurement of the crack face displacements normal to and tangential to the interface in the region of the crack front, using optical interferometry. A specially constructed loading device will be used to apply displacements normal and tangential to the interface, to the same degree of accuracy as the measurements of crack flank displacements. Such direct evaluations will then be used to determine the validity of linearized stress analyses (for static cracks) and local fracture criteria that govern the initiation and steady propagation of interface cracks.