Shear Properties of a Novel Class of Plastically Isotropic Mechanical Metamaterials with Discrete Assemblies

Mechanical metamaterials (MMs), characterized by their architectural geometries and exceptional mechanical properties, have garnered substantial interest due to their broad engineering potential. Although mechanical metamaterials have been widely studied under compression, bending, and impact, their shear properties—essential for torsion, lateral loading, and multidirectional stress states—are poorly understood. This study investigates the shear behavior of a novel class of discretely assembled thin-walled mechanical metamaterials (DATWMMs) - a plastically isotropic system inspired by traditional Chinese mortise-tenon structures and constructed through customized assembly of finite slender tubular components. Through an integrated experimental and computational approach, we systematically characterize the shear behavior of DATWMMs, elucidating the critical relationship between their architected geometry and mechanical performance. Our findings demonstrate that the discrete assembly strategy enables DATWMMs to achieve exceptional mechanical performance, including a specific shear modulus of 321 kN·m/kg and specific shear strength of 24 kN·m/kg, along with superior structural stability, while permitting precise property tuning through controlled variations in component size, cross-sectional geometry, and constituent materials. This work not only addresses a critical knowledge gap in mechanical metamaterials research by systematically characterizing their shear properties but also provides valuable insights for designing advanced materials with enhanced performance under shear-dominated loading scenarios.