An innovative Poisson's ratio (PR) sign-switching stiffness-changing mechanical metamaterial with potential applicability in automotive and construction industries is presented. The metamaterial that is designed by modifying and combining hexagonal and re-entrant unit cells is fabricated via additive manufacturing and explored using experiments and finite element analysis (FEA). The metamaterial shows excellent specific energy absorption (SEA) properties in comparison with the hexagonal lattice structure, exhibiting approximately 25% higher SEA. Parametric studies reveal that the auxeticity of the metamaterial and its PR sign-changing properties can be tuned by modifying the design parameters. Also, the load-carrying capacity of the metamaterial can be tuned along with its stiffness-changing properties by modifying the unit cell parameters. The geometric parameters of the internal concave unit cells significantly affect the auxeticity of the structure and the strains in which PR sign-switching and effective Young's modulus change take place. Finally, an enhanced form of the metamaterial is presented and analyzed via FEA, showing superior effective Young's modulus change ratio and improved stability under in-plane compression. The parametric studies show that the proposed metamaterial exhibits stiffness-changing property under transverse compression and PR sign-switching behaviour under transverse tension.

提出了一种创新的泊松比（PR）符号切换刚度改变机械超材料，在汽车和建筑行业具有潜在的适用性。通过修改和组合六边形和凹入晶胞而设计的超材料是通过增材制造制造的，并通过实验和有限元分析（FEA）进行探索。与六方晶格结构相比，超材料表现出优异的比能吸收 (SEA) 特性，SEA 高出约 25%。参数研究表明，可以通过修改设计参数来调整超材料的拉胀性及其 PR 符号变化特性。此外，可以通过修改晶胞参数来调整超材料的承载能力及其刚度变化特性。内部凹面晶胞的几何参数显着影响结构的拉胀性以及发生PR符号转换和有效杨氏模量变化的应变。最后，提出了超材料的增强形式并通过有限元分析进行分析，显示出优异的有效杨氏模量变化率和面内压缩下更高的稳定性。参数研究表明，所提出的超材料在横向压缩下表现出刚度变化特性，在横向拉伸下表现出 PR 符号切换行为。通过有限元分析提出并分析了超材料的增强形式，显示出优异的有效杨氏模量变化率和面内压缩下更高的稳定性。参数研究表明，所提出的超材料在横向压缩下表现出刚度变化特性，在横向拉伸下表现出 PR 符号切换行为。通过有限元分析提出并分析了超材料的增强形式，显示出优异的有效杨氏模量变化率和面内压缩下更高的稳定性。参数研究表明，所提出的超材料在横向压缩下表现出刚度变化特性，在横向拉伸下表现出 PR 符号切换行为。