Compliant cellular materials with compliant porous structures: A mechanism based materials design

Cellular materials have two important properties: structures and mechanisms. These properties have important applications in materials design; in particular, they are used to determine the modulus and yield strain. The objective of this study is to gain a better understanding of these two properties and to explore the synthesis of compliant cellular materials (CCMs) with compliant porous structures (CPSes) generated from modified hexagonal honeycombs. An in-plane constitutive CCM model is constructed using the strain energy method, which uses the deformation of hinges around holes and the rotation of links. A finite element (FE) based simulation is conducted to validate the analytical model. The moduli and yield strains of the CCMs with an aluminum alloy are about 5.8 GPa and 0.57% in one direction and about 2.9 MPa and 20% in the other direction. CCMs have extremely high positive and negative Poisson’s ratios (νxy∗ ∼ ±40±40) due to the large rotation of the link member in the transverse direction caused by an input displacement in the longitudinal direction. CCMs also show higher moduli after contact of slit edges at the center region of the CPSes. The synthesized CPSes can also be used to design a new CCM with a Poisson’s ratio of zero using a puzzle-piece CPS assembly. This paper demonstrates that compliant mesostructures can be used for next generation materials design in tailoring mechanical properties such as moduli, strength, strain, and Poisson’s ratios. The proposed mesostructures can also be easily manufactured using a conventional cutting method.