Unit Cell Synthesis for Design of Materials With Targeted Nonlinear Deformation Response

Abstract

A systematic unit cell synthesis approach is presented for designing metamaterials from a unit cell level, which are made out of linearly elastic constitutive materials to achieve tunable nonlinear deformation characteristics. This method is expected to serve as an alternative to classical Topology Optimization methods (solid isotropic material with penalization or homogenization) in specific cases by carrying out unit cell synthesis and subsequent size optimization (SO). The unit cells are developed by synthesizing elemental components with simple geometries that display geometric nonlinearity under deformation. The idea is to replace the physical nonlinear behavior of the target material by adding geometric nonlinearities associated with the deforming entities and thus, achieve large overall deformations with small linear strains in each deformed entity. A case study is presented, which uses the proposed method to design a metamaterial that mimics the nonlinear deformation behavior of a military tank track rubber pad under compression. Two unit cell concepts that successfully match the nonlinear target rubber compression curve are evaluated. Conclusions and scope for future work to develop the method are discussed.

The Influence of Material Property Variances and Printing Tolerances on the Mechanical Behavior of an Additively Manufactured Meta-Material Tank Track Backer Pad

“…The Unit Cell Synthesis Method is a meta-material design process presented by Satterfield et al (2017) and modified by Kulkarni (2016), which is intended to generate cellular based materials that exhibit nonlinear deformation under loading conditions. The method utilizes functional beam elements, arranged in either a series or parallel orientation, much like electrical elements or springs, to obtain general target responses.…”

Design of a Single Layer Metamaterial for Pressure Offloading of Transtibial Amputees

“…Optimizing the material coefficients is meant to act as a representation of optimizing the draft angle of the metamaterial. The idea of altering key parameters to guide the redesigning of unit cells was similar to the one used by Satterfield et al [63] who showed that altering parameters that represent the physical response of a unit cell can lead to similar results as altering the unit cell directly. The optimization of the material properties is described below.…”