标题： 二维晶体中的协同裂纹 显示英文标题

标题： Cooperating Cracks in Two-Dimensional Crystals

摘要： 极各向异性固体中多裂纹的模式发展，如双层或多层二维（2D）晶体，包含丰富的物理现象，然而这一领域仍大多未被探索。我们通过透射电子显微镜和分子动力学模拟研究了相邻2D层之间的裂纹相互作用。在双层2D晶体中，平行裂纹和反平行（'En-Passant'）裂纹分别相互吸引和排斥，这与共面裂纹的行为形成鲜明对比。我们表明，裂纹尖端周围面内位移场之间的失配导致非均匀的层间剪切，通过产生应力强度因子的反对称分量来改变裂纹驱动力。裂纹之间的跨层相互作用直接导致材料增韧，其强度随着剪切刚度的增加而增加，随着裂纹间距的减少而降低。基于实验结果和模拟结果，提出了一种将线弹性断裂力学理论和剪切滞后模型相结合的理论，该理论指导了非常规的方法来设计断裂模式并增强材料抗裂性能。 显示英文摘要

摘要： The pattern development of multiple cracks in extremely anisotropic solids such as bilayer or multilayer two-dimensional (2D) crystals contains rich physics, which, however, remains largely unexplored. We studied crack interaction across neighboring 2D layers by transmission electron microscopy and molecular dynamics simulations. Parallel and anti-parallel ('En-Passant') cracks attract and repel each other in bilayer 2D crystals, respectively, in stark contrast to the behaviors of co-planar cracks. We show that the misfit between in-plane displacement fields around the crack tips results in non-uniform interlayer shear, which modifies the crack driving forces by creating an antisymmetric component of the stress intensity factor. The cross-layer interaction between cracks directly leads to material toughening, the strength of which increases with the shear stiffness and decreases with the crack spacings. Backed by the experimental findings and simulation results, a theory that marries the theory of linear elastic fracture mechanics and the shear-lag model is presented, which guides the unconventional approach to engineer fracture patterns and enhance material resistance to cracking.