The propagation of in-plane shear cracks is investigated in brittle microstructured materials modeled by the constrained Cosserat elasticity. This theory introduces characteristic material lengths in order to describe the scale effects that emerge from the underlying microstructure and has proved to be very effective for modeling complex microstructured materials. An exact solution is obtained based on integral transforms and the Wiener-Hopf technique. Numerical results are presented illustrating the dependence of the stress intensity factor and the energy release rate upon the loading profile, the propagation velocity, and the characteristic material lengths of Cosserat elasticity. It is shown that depending on the Cosserat microstructural lengths the limiting crack propagation velocity can be significantly lower than the classical Rayleigh limit. Moreover, strengthening effects are observed when the characteristic material lengths become comparable to the geometrical lengths of the problem, a behavior that has been experimentally verified in fracture of ceramics.

在受约束的Cosserat弹性建模的脆性微结构材料中，研究了平面内剪切裂纹的扩展。该理论引入了特征材料的长度，以描述潜在的微观结构产生的尺度效应，并已证明对于建模复杂的微观结构材料非常有效。基于积分变换和Wiener-Hopf技术可获得精​​确的解决方案。数值结果表明应力强度因子和能量释放速率对载荷分布，传播速度和Cosserat弹性材料的特征长度的依赖性。结果表明，取决于Cosserat的微观结构长度，极限裂纹扩展速度可能大大低于经典的Rayleigh极限。