Distorting crack-front geometry for enhanced toughness by manipulating bioinspired heterogeneity

Kaijin Wu; Zhaoqiang Song; Mengqi Liu; Zewen Wang; Si-Ming Chen; Shu-Hong Yu; Linghui He; Yong Ni

doi:10.1038/s41467-024-55723-8

Distorting crack-front geometry for enhanced toughness by manipulating bioinspired heterogeneity

Nat Commun. 2025 Jan 2;16(1):194. doi: 10.1038/s41467-024-55723-8.

Authors

Kaijin Wu¹, Zhaoqiang Song², Mengqi Liu¹, Zewen Wang¹, Si-Ming Chen³, Shu-Hong Yu³, Linghui He¹, Yong Ni⁴

Affiliations

¹ 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.
² Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA, USA.
³ Division of Nanomaterials & Chemistry, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, China.
⁴ 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. [email protected].

Abstract

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.

Abstract

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