Crack propagation at material interfaces: II experiments on mode interaction
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Optical interferometry is used to measure crackopening profiles for interfacial cracks in a model adhesive joint. Application of boundary displacements with a resolution of 0.16 μm is achieved through a combination of thermal expansions and optical control in a servo loop. The degree of nonlinear deformation accompanying small levels of normal and shear strain across the bond is documented, and crackfront displacement fields are exploited to evaluate possible criteria for crack growth under combined normal and shear loading. Within the accuracy afforded by the crack-propagation investigation it appears that crack growth is governed by the vectorial crack-tip displacements, namely by the vector sum of the local normal and tangential displacement components. In the limit of infinitesimal strains this criterion reduces to the strain energy-release-rate criterion of linear fracture mechanics.
KeywordsShear Strain Interfacial Crack Shear Loading Displacement Component Adhesive Joint
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