High speed crack propagation in bi-phase materials: an experimental study

Compliance and strain energy release rate of homogeneous and interleaved end-notched flexure specimens for mode II fracture characterization are investigated with shear deformation beam theory and finite element analysis. Interleaving refers to a thin layer of polymer film being placed at the midplane of the beam. Analytical results are correlated with numerical finite element results for a wide range of interleaf thicknesses. The finite element results revealed that the compliance and energy release rate remained virtually the same whether the crack was within the interlayer or between the interlayer and the composite. Furthermore, within the accuracy of the numerical modeling, the asymmetric crack configuration did not render the specimen mixed mode, (G_I=0). Close agreement was observed between sandwich beam theory and finite element analysis.