Lightweight and reusable materials are desired in engineering for mitigating repetitive impacts. However, the limitation of mitigation efficiency is always a problem in spite of various materials have been studied. And other issues need to be improved, such as bulky and poor load-bearing. There still exists challenge to design a reusable impact mitigation material with high efficient, lightweight and high stiffness. Here, a lightweight syndiotactic chiral metamaterial (SCM) with compression-torsion coupling effect (CTCE) is proposed and fabricated for repetitive impact mitigation. Impact experiments indicate that the proposed metamaterials exhibit significant superiorities in impact mitigation efficiency, lightweight, higher stiffness and less cells over the previously reported ones. In order to reveal the deeper mechanism of the superior properties, the band gaps of SCM with CTCE and isometric chiral metamaterial (ICM) without CTCE are analyzed and compared by transmissibility tests and numerical simulations. It is found that the extra energy dissipated by torsion caused by CTCE is the key factor for excellent mitigation performance, which enlarges the band gap to low-frequencies and prevents more waves pass through. To balance the mitigation performance and load carrying capacity, the gradient design strategy is proposed to cope with large impact loads with maintaining high mitigation efficiency, which is achieved by overlapping the band gaps of different cells to widen the band gap range. The mechanism of improving impact mitigation performance by CTCE revealed in the present work enlightens a new avenue to develop effective, reusable and lightweight buffer materials.

中文翻译：

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基于压扭耦合机制的高效、可重复使用的冲击缓冲超材料

在工程中需要轻质且可重复使用的材料来减轻重复性影响。然而，尽管已经研究了各种材料，但缓解效率的限制始终是一个问题。还有体积大、承重差等问题需要改进。设计一种高效、轻质、高刚度的可重复使用的冲击缓冲材料仍然存在挑战。在这里，提出并制造了一种具有压缩扭转耦合效应（CTCE）的轻质间规手性超材料（SCM），用于减轻重复冲击。冲击实验表明，与之前报道的超材料相比，所提出的超材料在冲击缓解效率、轻质、更高的刚度和更少的单元方面表现出显着的优势。为了揭示其优越性能的更深层次机制，通过透射率测试和数值模拟对采用CTCE的SCM和不采用CTCE的等距手性超材料（ICM）的带隙进行了分析和比较。研究发现，CTCE 引起的扭转所耗散的额外能量是优异缓解性能的关键因素，它将带隙扩大到低频并阻止更多的波通过。为了平衡缓解性能和承载能力，提出了梯度设计策略，以应对大冲击载荷并保持高缓解效率，这是通过重叠不同单元的带隙以加宽带隙范围来实现的。目前的工作揭示了 CTCE 提高冲击缓解性能的机制，为开发有效、可重复使用和轻质缓冲材料开辟了新途径。