Impact resistant hierarchically structured materials based on fruit walls and nut shells

果壁、坚果壳和种子壳通常具有多种功能。其中之一是直接或间接地保护种子不受机械损害或其他不利环境影响，这使生物结构成为开发新材料和部件的榜样，保护商品和/或人免受例如粗暴搬运或碰撞造成的损害。我们的目标是通过在不同的层次上改变金属泡沫组件的结构来改善其机械性能，这些结构受到对我们的角色模型的冲击和/或穿刺性非常重要的特征和原则的启发，而不是通过调整块状材料的属性来实现。为此，我们建立了多种研究方法，将力学测试与不同的成像方法相结合。我们确定了不同的结构层次对于生物角色模型的机械变形和破坏行为特别重要。我们将这些抽象并转化为相应的结构原理，从而设计出具有层次化结构的仿生金属泡沫。在第一个项目期间通过熔模铸造成功生产了第一个金属基仿生结构后，在过去两年中对工艺进行了修改和优化，以实现更复杂和更可靠的结构，通过实施和组合不同的层次结构元素以及最大限度地减少铸造缺陷。为了评估结构效应，我们采用了与生物角色模型类似的调查方法和力学测试实验。在申请项目第三阶段，我们将进一步追求这一目标，对生物概念生成器在更深层次和更高层次上的形式-结构-功能关系有更深入的定量了解，并将这些发现抽象出来，转移到具有进一步改善的减振性能和抗穿刺性的仿生金属泡沫和复合泡沫结构中。

Fruit walls as well as nut and seed shells typically perform a multitude of functions. One of these 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 rough handling or crashes. Our goal is to improve the mechanical properties of metal foam based components by altering their structure on various hierarchical levels inspired by features and principles important for the impact and/or puncture resistance of our role models, rather than by tuning the properties of the bulk material. For this we have established various investigation methods which combine mechanical testing with different imaging methods. We identified different structural hierarchies to be especially important for the mechanical deformation and failure behaviour of the biological role models. We abstracted and transferred these into corresponding structural principles and thus designed hierarchically structured bio-inspired metal foams. After the successful production of first metal based bio-inspired structures by investment casting during the 1st project period, the process has been modified and optimised within the last two years in order to realise more complex and more reliable structures, by implementing and combining different hierarchical structural elements as well as by minimising casting defects. To evaluate the structural effects, we applied similar investigation methods and mechanical testing experiments as those used for the biological role models. In the applied for project phase 3 we will further pursue this goal by gaining an even deeper quantitative understanding of the form-structure-function relationship of the biological concept generators on deeper hierarchical levels and level overarching, and by abstracting these findings and transferring them in bio-inspired metal foams and composite foam-based structures with further improved damping properties and puncture resistance.