Institute of Advanced Ceramics, Hamburg University of Technology, D 21073 Hamburg, Germany.
Institute of Advanced Ceramics, Hamburg University of Technology, D 21073 Hamburg, Germany.
Dent Mater. 2018 Jan;34(1):69-77. doi: 10.1016/j.dental.2017.11.007. Epub 2017 Nov 23.
This article investigates the mechanical properties of a material with hierarchically arranged microcracks.
Hierarchically structured biomaterials such as enamel exhibit superior mechanical properties as being stiff and damage tolerant at the same time. The common mechanical explanation for this behavior is based on the hierarchically structured arrangement of hard minerals and soft organics and their cooperative deformation mechanisms. In situ mechanical experiments with mm-sized bovine enamel bending bars an scanning electron microscope reveal that enamel is able to withstand mechanical loading even if it contains microcracks on different lengths scales. To clarify this issue an analytical hierarchical microcrack model of non-interacting cracks is presented.
The model predicts a decrease of the elastic modulus and the fracture strength with increasing levels of hierarchy. The fracture strain on the other hand may decrease or increase with the number of hierarchical levels, depending on the microcrack density. This simple hierarchical microcrack model is able to explain already published experiments with focused ion beam prepared μm-sized enamel cantilevers on different hierarchical levels. In addition it is shown that microcracking during loading in hierarchical materials may lead to substantial pseudoplastic behavior.
本文研究了具有层次状微裂纹的材料的力学性能。
具有层次结构的生物材料，如牙釉质，具有同时坚硬和耐损伤的优异力学性能。这种行为的常见力学解释基于硬矿物质和软有机物的层次结构排列及其协同变形机制。使用毫米级牛牙釉质弯曲棒和扫描电子显微镜进行原位力学实验表明，即使牙釉质含有不同长度尺度的微裂纹，它也能够承受机械载荷。为了澄清这个问题，提出了一个非相互作用裂纹的分析层次微裂纹模型。
该模型预测随着层次的增加，弹性模量和断裂强度降低。另一方面，断裂应变可能随着层次数量的增加而增加或减少，这取决于微裂纹密度。这个简单的层次微裂纹模型能够解释已经发表的关于不同层次聚焦离子束制备的微米级牙釉质悬臂梁的实验。此外，还表明在层次材料加载过程中的微裂纹可能导致显著的假塑性行为。
