近日，瑞士洛桑联邦理工学院的John M. Kolinski及其研究团队取得一项新进展。经过不懈努力，他们发现裂纹前缘几何形状的复杂性能够提高脆性固体的韧性。相关研究成果已于2024年3月22日在国际知名学术期刊《自然—物理学》上发表。

该研究团队运用光学显微镜技术，对多种透明脆性材料（涵盖四种不同化学特性的水凝胶和弹性体）进行了深入的三维表征，以精确描绘复杂裂纹前沿的裂纹尖端运动学特征。研究结果显示，驱动裂纹扩展所需的临界应变能与裂纹的测地线长度呈现出显著的正比关系，这一现象使得样本在实际应用中表现出更高的韧性。

裂纹前缘的几何形态与材料韧性之间的紧密联系，对三维裂纹理论建模产生了深远影响。这种联系不仅贯穿于材料的工程测试过程，更延伸至新材料的从头开发阶段。同时，这也凸显了当前三维裂纹理论的一个重要空白。

据悉，脆性固体常常因表面缺陷导致的裂纹生长与扩展而失效。线弹性断裂力学是建模这一过程的关键工具，它利用临界应力强度因子或奇异应力场的前因子来量化材料的韧性。虽然这一理论在平面裂纹的研究中得到了广泛应用，但现实情况中裂纹往往具有复杂的几何形状，并不符合平面假设，从而违背了线弹性断裂力学的核心原则。

附：英文原文

Title: Complexity of crack front geometry enhances toughness of brittle solids

Author: Wei, Xinyue, Li, Chenzhuo, McCarthy, Can, Kolinski, John M.

Issue&Volume: 2024-03-22

Abstract: Brittle solids typically fail by growth and propagation of a crack from a surface flaw. This process is modelled using linear elastic fracture mechanics, which parameterizes the toughness of a material by the critical stress intensity factor, or the prefactor of the singular stress field. This widely used theory applies for cracks that are planar, but cracks typically are not planar, and instead are geometrically complex, violating core tenets of linear elastic fracture mechanics. Here we characterize the crack tip kinematics of complex crack fronts in three dimensions using optical microscopy of several transparent, brittle materials, including hydrogels of four different chemistries and an elastomer. We find that the critical strain energy required to drive the crack is directly proportional to the geodesic length of the crack, which makes the sample effectively tougher. The connection between crack front geometry and toughness has repercussions for the theoretical modelling of three-dimensional cracks, from engineering testing of materials to ab-initio development of novel materials, and highlights an important gap in the current theory for three-dimensional cracks.

DOI: 10.1038/s41567-024-02435-x

Source: https://www.nature.com/articles/s41567-024-02435-x