Lightweight materials used for impact mitigation must be able to resist impact and absorb the maximum amount of energy from the impactor. Auxetic materials have the potential to achieve high resistance by drawing material into the impact zone and providing higher indentation and shear resistance. However, these materials must be artificially designed, and the large deformation dynamic effects of the created structures must be taken into consideration when deciding on a protection concept. Despite their promise, little attention has been given to understanding the working mechanisms of high-rate and finite deformation effects of architected auxetic lattice structures. This study compares the static and dynamic elastic properties of different auxetic structures with a honeycomb structure, a typical non-auxetic lattice, at equivalent mass and stiffness levels. In this study, we limit the investigation to elastic material behavior and do not consider contact between the beams of the lattices. It is demonstrated that the equivalent static and dynamic properties of individual lattices at an undeformed state are insufficient to explain the variations observed in impact situations. In particular, the initial Poisson’s ratio does not determine the ability of a structure to resist impact. To gain a thorough comprehension of the overall behavior of these structures during localized, high rate compression, the evolution of the elastic tangent properties under compression and shear deformation was monitored, leading to a more profound understanding. Observations made in one configuration of stiffness and mass are replicated and analyzed in related configurations.

中文翻译：

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建筑拉胀超材料中影响缓解的几何效应

用于减轻冲击的轻质材料必须能够抵抗冲击并吸收来自冲击器的最大能量。拉胀材料有可能通过将材料拉入冲击区域并提供更高的压痕和剪切阻力来实现高阻力。然而，这些材料必须是人工设计的，并且在决定保护概念时必须考虑所创建结构的大变形动力效应。尽管他们做出了承诺，但很少有人关注理解建筑拉胀晶格结构的高速和有限变形效应的工作机制。本研究将不同拉胀结构与蜂窝结构（一种典型的非拉胀晶格）在等效质量和刚度水平下的静态和动态弹性特性进行了比较。在本研究中，我们将研究限制于弹性材料行为，并且不考虑晶格梁之间的接触。结果表明，未变形状态下各个晶格的等效静态和动态特性不足以解释在撞击情况下观察到的变化。特别是，初始泊松比并不能决定结构抵抗冲击的能力。为了全面了解这些结构在局部高速压缩过程中的整体行为，监测了压缩和剪切变形下弹性切线特性的演变，从而获得更深刻的理解。在一种刚度和质量配置中进行的观察在相关配置中得到复制和分析。