As one of the most popular 3D printed metamaterials, the auxetic structure with its tunable Poisson’s ratio has attracted huge amount of attention recently. In this study, we designed an auxetic shape-memory metamaterial, which showed designable buckling responses by using the thermomechanically coupled in-plane instability. The influence of viscoelasticity on in-plane moduli and Poisson’s ratios of shape-memory auxetic metamaterial was experimentally investigated. Based on the generalized Maxwell model and finite-element method, the buckling behaviors and their main influence factors were studied. The analytical results and experimental ones showed a good agreement. Thermomechanical properties of the printed metamaterials govern the temperature and strain rate-dependent buckling, and a controllable transition from the negative to positive Poisson’s ratio in the metamaterials can be achieved. Based on the shape memory effect, the buckled state and the Poisson’s ratio of the metamaterials can be tuned by programmed thermomechanical processes. This study provides a simple and efficient way to generate morphing structures using the designable buckling effect.

中文翻译：

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面向可设计屈曲的拉胀形状记忆超材料的 3D 打印

作为最流行的3D打印超材料之一，具有可调泊松比的拉胀结构最近引起了极大的关注。在这项研究中，我们设计了一种拉胀形状记忆超材料，该材料通过使用热机械耦合的面内不稳定性显示出可设计的屈曲响应。实验研究了粘弹性对形状记忆拉胀超材料的面内模量和泊松比的影响。基于广义麦克斯韦模型和有限元法，研究了屈曲行为及其主要影响因素。分析结果与实验结果吻合较好。印刷超材料的热机械特性决定了与温度和应变率相关的屈曲，并且可以实现超材料中从负泊松比到正泊松比的可控转变。基于形状记忆效应，超材料的屈曲状态和泊松比可以通过程序化的热机械过程进行调整。本研究提供了一种使用可设计屈曲效应生成变形结构的简单有效的方法。