[论文解读] Multilayered Recoverable Sandwich Composite Structures with Architected Core

Vinay Damodaran, Anna G. Hahm+1 more|arXiv (Cornell University)|Apr 25, 2021

Advanced Materials and Mechanics参考文献 42被引用 5

一句话总结

本文提出了一种多层可恢复的夹层复合结构，其3D打印的仿生芯材由粘弹性材料制成的中空截锥单元胞构成。芯材通过受控屈曲耗散能量，并通过伪双稳态恢复至原始形状，实现反复能量吸收而无永久变形或外部刺激。

ABSTRACT

In this paper, we propose a novel design and fabrication strategy to produce architected core structures for use as the core in composite sandwich structures. A traditional foam core or honeycomb structure is lightweight and stiff, but susceptible to permanent deformation when subjected to excessive loading. Here we propose the use of an architected structure composed of arrays of hollow truncated cone unit cells that dissipate energy and exhibit structural recovery. These structures printed with a viscoelastic material rely on buckling of their sidewalls to dissipate energy and snap-back to prevent permanent deformation. We explore the mechanical response of these conical unit cells in terms of their buckling strength and post-buckling stability condition, and develop design maps for the same, by relating them to non-dimensional geometric parameters $\alpha$, $\beta$, $\gamma$, where $\alpha$ represents the slenderness of the curved sidewalls, $\beta$ is the angle of the sidewall to the base, and $\gamma$ represents the curvature of the sidewall. A validated finite element model is developed and used to investigate the effect of these parameters. We see that the peak buckling load is directly proportional to both $\alpha$ & $\beta$ and is not dependent on $\gamma$ when the load is normalized by the volume of material in the curved sidewall. Interestingly, the post-buckling stability is influenced by $\gamma$, or the initial curvature of the sidewall, where a larger radius of curvature makes the structure less susceptible to exhibit structural bistability. The structures presented here are printed using a viscoelastic material, that causes them to exhibit pseudo-bistability, or a time-delayed recovery. This allows the structures to buckle and dissipate energy, and then recover to their original configurations without the need for external stimuli or energy.

研究动机与目标

• 开发一种可恢复的夹层复合芯材，兼具高能量耗散能力与在过载后的结构恢复能力。
• 解决传统泡沫或蜂窝芯材在冲击或过载下发生永久变形的局限性。
• 研究仿生截锥单元胞在轴向及轴向-剪切组合载荷下的力学行为。
• 识别控制屈曲强度与屈曲后稳定性的几何参数，以实现最优设计。
• 证明粘弹性材料行为可实现时间延迟恢复（伪双稳态），从而消除对外部刺激的依赖。

提出的方法

• 使用粘弹性树脂设计并3D打印中空截锥单元胞，以实现能量耗散与延迟恢复。
• 定义无量纲几何参数：α（侧壁细长比）、β（倾斜角与底面夹角）和γ（周向曲率）。
• 采用有限元模拟（FEM）分析轴向及轴向-剪切组合载荷，结果与实验数据进行验证。
• 对单层和双层样品进行三点弯曲试验，评估结构恢复性与变形行为。
• 分析载荷-位移曲线与位移-时间响应，量化恢复动力学与稳定性。
• 建立设计图谱，关联α、β和γ与屈曲载荷及屈曲后稳定性，实现预测性设计。

实验结果

研究问题

• RQ1 几何参数α、β和γ如何影响截锥单元胞的峰值屈曲载荷与屈曲后稳定性？
• RQ2 粘弹性在实现伪双稳态行为与时间延迟结构恢复中起什么作用？
• RQ3 轴向-剪切组合载荷如何影响仿生芯材结构的恢复行为？
• RQ4 多层化是否可在显著减轻重量惩罚的前提下提升承载能力与弯曲刚度？
• RQ5 曲率参数γ在何种程度上控制从单稳态向伪双稳态行为的转变？

主要发现

• 峰值屈曲载荷与α（细长比）和β（倾斜角）成正比，当按材料体积归一化后，与γ无关。
• 屈曲后稳定性受γ显著影响；γ值越大（曲率半径越小），越易产生“锁定”效应，从而增强伪双稳态性能。
• 实验三点弯曲测试证实，单层与双层样品均实现完全恢复，恢复时间在位移-时间曲线中可观察到。
• 加载过程中的侧向（剪切）位移在锥体远端产生恢复性拉力，驱动自恢复并促进单稳态行为。
• 粘弹性材料实现伪双稳态，使结构可暂时保持变形状态，并在延迟后无需外部刺激即可恢复。
• 芯材多层化可实现单元胞更密集排列，提升弯曲刚度与承载能力，同时保持较低的重量增加。