Bührig-Polaczek A, Fleck C, Speck T, Schüler P, Fischer S F, Caliaro M, Thielen M
Foundry-Institute, RWTH Aachen University, Aachen, Germany.
Bioinspir Biomim. 2016 Jul 19;11(4):045002. doi: 10.1088/1748-3190/11/4/045002.
Fruit walls as well as nut and seed shells typically perform a multitude of functions. One of the biologically most important functions consists in the direct or indirect protection of the seeds from mechanical damage or other negative environmental influences. This qualifies such biological structures as role models for the development of new materials and components that protect commodities and/or persons from damage caused for example by impacts due to rough handling or crashes. We were able to show how the mechanical properties of metal foam based components can be improved by altering their structure on various hierarchical levels inspired by features and principles important for the impact and/or puncture resistance of the biological role models, rather than by tuning the properties of the bulk material. For this various investigation methods have been established which combine mechanical testing with different imaging methods, as well as with in situ and ex situ mechanical testing methods. Different structural hierarchies especially important for the mechanical deformation and failure behaviour of the biological role models, pomelo fruit (Citrus maxima) and Macadamia integrifolia, were identified. They were abstracted and transferred into corresponding structural principles and thus hierarchically structured bio-inspired metal foams have been designed. A production route for metal based bio-inspired structures by investment casting was successfully established. This allows the production of complex and reliable structures, by implementing and combining different hierarchical structural elements found in the biological concept generators, such as strut design and integration of fibres, as well as by minimising casting defects. To evaluate the structural effects, similar investigation methods and mechanical tests were applied to both the biological role models and the metallic foams. As a result an even deeper quantitative understanding of the form-structure-function relationship of the biological concept generators as well as the bio-inspired metal foams was achieved, on deeper hierarchical levels and overarching different levels.
果实壁以及坚果和种子壳通常具有多种功能。生物学上最重要的功能之一是直接或间接保护种子免受机械损伤或其他负面环境影响。这使这些生物结构成为开发新材料和部件的典范，这些新材料和部件可保护商品和/或人员免受例如因粗暴处理或碰撞造成的冲击所导致的损坏。我们能够证明，受对生物典范的抗冲击和/或抗穿刺至关重要的特征和原理启发，通过在不同层次水平上改变基于金属泡沫的部件的结构，而非调整块状材料的性能，就可以改善其机械性能。为此，已经建立了各种研究方法，这些方法将机械测试与不同的成像方法以及原位和非原位机械测试方法相结合。确定了对生物典范——柚子（Citrus maxima）和澳洲坚果（Macadamia integrifolia）的机械变形和失效行为特别重要的不同结构层次。对它们进行了抽象并转化为相应的结构原理，从而设计出了具有层次结构的仿生金属泡沫。成功建立了一种通过熔模铸造生产金属基仿生结构的路线。这使得通过实施和组合在生物概念生成器中发现的不同层次结构元素（如支柱设计和纤维整合），以及通过最小化铸造缺陷来生产复杂且可靠的结构成为可能。为了评估结构效果，对生物典范和金属泡沫都应用了类似的研究方法和机械测试。结果，在更深层次和总体不同层次上，对生物概念生成器以及仿生金属泡沫的形式 - 结构 - 功能关系有了更深入的定量理解。
