Department of Mechanical Engineering, Northwestern University, Evanston, IL 60062, USA.
Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093, USA; Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, People's Republic of China.
J Mech Behav Biomed Mater. 2017 Dec;76:30-37. doi: 10.1016/j.jmbbm.2017.06.009. Epub 2017 Jun 10.
Pangolin scales form a durable armor whose hierarchical structure offers an avenue towards high performance bio-inspired materials design. In this study, the fracture resistance of African pangolin scales is examined using single edge crack three-point bend fracture testing in order to understand toughening mechanisms arising from the structures of natural mammalian armors. In these mechanical tests, the influence of material orientation and hydration level are examined. The fracture experiments reveal an exceptional fracture resistance due to crack deflection induced by the internal spatial orientation of lamellae. An order of magnitude increase in the measured fracture resistance due to scale hydration, reaching up to ~ 25kJ/m was measured. Post-mortem analysis of the fracture samples was performed using a combination of optical and electron microscopy, and X-ray computerized tomography. Interestingly, the crack profile morphologies are observed to follow paths outlined by the keratinous lamellae structure of the pangolin scale. Most notably, the inherent structure of pangolin scales offers a pathway for crack deflection and fracture toughening. The results of this study are expected to be useful as design principles for high performance biomimetic applications.
穿山甲鳞片形成了一种耐用的盔甲，其层次结构为高性能仿生材料设计提供了一个途径。在这项研究中，通过单边裂纹三点弯曲断裂试验来研究非洲穿山甲鳞片的抗断裂能力，以了解源自天然哺乳动物盔甲结构的增韧机制。在这些机械测试中，研究了材料取向和水合水平的影响。断裂实验由于鳞片层的内部空间取向引起的裂纹偏转，显示出异常高的抗断裂能力。由于鳞片的水合作用，测量的抗断裂阻力增加了一个数量级，达到约 25kJ/m。使用光学显微镜和电子显微镜以及 X 射线计算机断层扫描对断裂样品进行了死后分析。有趣的是，观察到裂纹轮廓形态遵循穿山甲鳞片角蛋白层结构所概述的路径。值得注意的是，穿山甲鳞片的固有结构为裂纹偏转和断裂韧性提供了途径。本研究的结果有望为高性能仿生应用的设计原则提供有用的信息。
