With the development of structural metamaterials and 3D printing technology, the polymorphic shape-memory metamaterials have attracted extensive attention. This study aims to design a structural 3D printed shape-memory metamaterial, of which the epigenetic bi-stability of shape-fixity and recovery behaviors have been achieved by means of the dual matching nominal moduli and geometrical size optimization. Epigenetic bi-stability and dual matching refer to the combination of bi-materials in a specific structure, in response to external stimuli to show adjustable bi-stability. Elastic thermoplastic polyurethane (TPU) and viscoelastic polylactic acid (PLA) both are thermally responsive shape-memory polymers (SMPs) and have been employed to fabricate the structural metamaterial, of which the nominal modulus is tailorable owing to the dual matching shape-memory effects (SMEs) of two SMP components. Furthermore, the effects of structural parameters, i.e., width of framework and width of internal support, on the nominal modulus have been investigated for the structural metamaterials, of which the shape-fixity and recovery ratios have been characterized using finite element method (FEM) analyses and experimental measurements. Finally, a constitutive relationship among structural parameters, dual matching SME and nominal modulus has been identified to explore the working principle of epigenetic bi-stability in shape-memory metamaterials. This study provides a design strategy for a shape-memory metamaterial with a post-switchable bi-stability, through dual matching SME and geometrical size optimization.

随着结构超材料和3D打印技术的发展，多态形状记忆超材料引起了广泛的关注。本研究旨在设计一种结构3D打印形状记忆超材料，通过双重匹配名义模量和几何尺寸优化，实现了形状固定和恢复行为的表观遗传双稳定性。表观遗传双稳定性和双重匹配是指双材料在特定结构中的组合，响应外界刺激而表现出可调节的双稳定性。弹性热塑性聚氨酯（TPU）和粘弹性聚乳酸（PLA）都是热响应形状记忆聚合物（SMP），已被用来制造结构超材料，由于双重匹配的形状记忆效应，其标称模量是可定制的（中小企业）两个 SMP 组件。此外，还研究了结构参数（即框架宽度和内部支撑宽度）对结构超材料标称模量的影响，并使用有限元法（FEM）对其形状固定性和恢复率进行了表征分析和实验测量。最后，确定了结构参数、双重匹配SME和标称模量之间的本构关系，以探索形状记忆超材料表观遗传双稳定性的工作原理。本研究通过双重匹配 SME 和几何尺寸优化，为具有后切换双稳定性的形状记忆超材料提供了一种设计策略。