Cellular solids are widely used in aerospace and transportation industries and have long been shown to possess some unique performance, such as lightweight, high stiffness, and strength. As advanced fabrication technologies develop, it is feasible to manufacture cellular mechanical metamaterials (CMMS) with speed and precision. CMMs are formed by periodically arranged basic unit cells and their properties are primarily based on their structural architecture rather than the consistent properties determined by the chemical composition. &nbsp;In order to design CMMs, it is necessary to explore the relationship between the mechanical effective properties, such as Young’s modulus and Poisson’s ratio, and the complex micro-structure of periodical unit cells (PUCs). Therefore, the investigation of the structure-property relationships of CMMs is an important step towards enabling their inverse design that aims to find the unique PUC structures that can provide the prescribed effective properties.&nbsp;Traditionally, the design of metamaterials highly requires the researchers’ rich experience with target materials and is limited in a small design space. Topology optimization is now employed as the most common method to design periodic unit cells (PUCs), which has long been recognized as a powerful tool for the optimization of both structures and materials. This freedom promotes the expansion of the design space and provides the optimization method with the ability to generate innovative structural layouts with high performance. The&nbsp;objective of this presentation/paper is to introduce a systematic and scientific framework to solve the inverse design problem of CMMs by optimizing the material distribution within a given design domain, which can satisfy the user-defined target effective properties under certain prescribed constraints.&nbsp;In this presentation/paper, Young’s modulus and Poisson’s ratio are two main effective properties we focus on in the multiscale design problem. The genetic algorithm (GA) is employed to synthesize the micro-structure of PUCs such that the difference between the predicted and target effective properties is minimized. The mechanical responses of CMMs are analyzed by direct numerical method (DNS) and homogenization method for two different scales of CMMs’ specimen, respectively. The responses are utilized to evaluate the fitness function of GA, which is corresponding to the difference between the predicted and target effective properties of the specimen. For the CMMs with a small number of PUCs, the DNS is applied to the whole specimen with the finite element method (FEM). However, when the size of the specimen is much larger than the PUCs, the DNS can become highly complex and time-consuming. In this case, the subject of FEM can be reduced into a representative volume element (RVE), which is defined as a minimum volume that can represent the mechanical behavior of the whole specimen. The homogenization method is applied to the RVE to predict the macroscopic properties of the specimen as a function of the underlying micro-structures. The final optimum micro-structures of porous metamaterials are expected to satisfy the pre-defined design requirements for mechanical performance.&nbsp;

Inverse Multiscale Design of Cellular Mechanical Metamaterials

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.