Mechanical metamaterials with 3D compliant porous structures

We propose compliant cellular material (CCM), a mechanical metamaterial, with compliant porous structure (CPS) generated from a modified hexagonal topology. The objective of this study is to explore the synthesis of three-dimensional (3D) CCMs with CPSes and to understand the mechanical behaviors of CCMs. An orthotropic constitutive model of CCMs is constructed using the strain energy method, which uses the deformation of hinges around holes and rotation of links. Nonlinear behavior of a finite element (FE) based simulation is conducted to validate the analytical model. The moduli and yield strains of the 3D CCMs with an aluminum alloy are about 1.2 GPa and 0.4% in the longitudinal direction and about 0.08 MPa and 30% in the lateral direction. The CCMs have extremely high positive and negative Poisson’s ratios (νxy∗∼±30) due to the large rotation of the link member in the transverse direction caused by an input displacement in the longitudinal direction. This paper demonstrates that compliant mesostructures can be used for next generation’s mechanical metamaterials design in tailoring mechanical properties such as modulus, strength, yield strain, and Poisson’s ratios.