Optimal design of Shellular, a micro-architectured material with ultralow density

Recently, a new ultralow-density materialwith micro-architecture, Shellular was introduced. Shellular consists of continuous smooth shells and has a typical hierarchical architecture across multiple scales. In this work, an optimal design for Shellular is sought in a simplified as well as realistic configuration for the maximum possible strength or modulus for a given density. After a series of analyses and design processes such as the selection of key geometrical parameters, the derivation of empirical equations, failure analysis, and corresponding optimization, optimized models were produced that are expected to have strengths about 2.5 times and Young's moduli about 4 times as high as those of the prior non-optimized Shellular specimens. Specifically, the optimized model of thin Ni shells with relative density of 0.002 and inclination angle of 60 degrees could gain the strength of 0.1 MPa and the Young's modulus of 5.06 MPa. However, to achieve the highest mechanical properties among the competitors in ultralow density domain, a more radical approach needs to be applied to the geometrical optimization of Shellular. (C) 2016 Elsevier Ltd. All rights reserved.