Interaction of shear cracks in microstructured materials modeled by couple-stress elasticity

The interaction of two colinear in-plane shear cracks is investigated within the context of couple-stress elasticity. This theory introduces characteristic material length scales that emerge from the underlying microstructure and has proved to be very effective for modeling complex microstructured materials. An exact solution of the boundary value problem is obtained through integral transforms and singular integral equations. The main goal is to explain the size effects that are experimentally observed in fracture of brittle microstructured materials. Two basic configurations are considered: a micro-macrocrack interaction, and a micro-microcrack interaction. Numerical results are presented illustrating the effects of couple-stresses on the stress intensity factor and the energy release rate. It is shown that significant deviations from the predictions of the standard LEFM occur when the geometrical lengths of the problem become comparable to the characteristic material length of the couple-stress theory revealing that in such cases it is inadequate to analyze fracture problems employing only classical elasticity considerations.