Wu Kaijin, Song Zhaoqiang, Liu Mengqi, Wang Zewen, Chen Si-Ming, Yu Shu-Hong, He Linghui, Ni Yong
CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, CAS Center for Excellence in Complex System Mechanics, University of Science and Technology of China, Hefei, Anhui, China.
Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA, USA.
Nat Commun. 2025 Jan 2;16(1):194. doi: 10.1038/s41467-024-55723-8.
Control of crack propagation is crucial to make tougher heterogeneous materials. As a crack interacts with material heterogeneities, its front distorts and adopts complex tortuous configurations. While the behavior of smooth cracks with straight fronts in homogeneous materials is well understood, the toughening by rough cracks with tortuous fronts in heterogeneous materials remains unsolved. Here we highlight a distorted crack-front geometric toughening mechanism by manipulating bioinspired anisotropic heterogeneities of microstructural orientations and component properties. We reveal theoretically and demonstrate experimentally that the local mixed-mode I + II + III fracture triggered by local anisotropic heterogeneities lead to a helical crack front in a representative heterogeneous system with bioinspired twisted plywood structures under remote mode I loading. An anomalous nonlinear law of both the enhanced fracture resistance and the helical crack-front length versus the microstructural orientation is revealed, in contrast to the linear toughening law ignoring the hidden 3D topography within crack fronts. An optimization design protocol towards toughness amplification is developed by parametrically manipulating anisotropic heterogeneities to helically distort crack front. Our findings not only provide physical insights into the origin of biological heterogeneities modulated tortuous crack fronts but also offer a benchmark solution for enhancing toughness by parametrically engineering spatial heterogeneities.
控制裂纹扩展对于制造更坚韧的非均质材料至关重要。当裂纹与材料的非均质性相互作用时，其前沿会发生扭曲并呈现出复杂的曲折形态。虽然均质材料中具有直线前沿的光滑裂纹的行为已得到很好的理解，但非均质材料中具有曲折前沿的粗糙裂纹的增韧问题仍未解决。在此，我们通过操纵受生物启发的微观结构取向和组分特性的各向异性非均质性，突出一种扭曲裂纹前沿几何增韧机制。我们从理论上揭示并通过实验证明，在远程I型加载下，由局部各向异性非均质性引发的局部I + II + III型混合模式断裂会导致具有受生物启发的扭曲胶合板结构的代表性非均质系统中出现螺旋裂纹前沿。与忽略裂纹前沿内隐藏的三维形貌的线性增韧定律相反，揭示了增强的抗断裂性和螺旋裂纹前沿长度与微观结构取向的反常非线性定律。通过参数化操纵各向异性非均质性以使裂纹前沿螺旋扭曲，开发了一种韧性放大的优化设计方案。我们的发现不仅为生物非均质性调节曲折裂纹前沿的起源提供了物理见解，还为通过参数化工程空间非均质性提高韧性提供了基准解决方案。
