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.
Keywords
Cosserat media, energy release rate, micro-macrocrack
interaction, crack shielding, microstructure
