Selection of periodic cellular structures for multifunctional applications directly based on their unit cell geometry

Abstract

Although the use of periodic cellular structures for multifunctional applications by designing their unit cell topology has been demonstrated, every unit cell candidate is currently tested for individual functional performance by computational modeling, a cumbersome approach. This study addresses this design limitation by demonstrating a geometry-based approach for rapid selection of the unit cell for mechanical-thermal-acoustics applications. Three geometric parameters of the unit cell, viz., porosity, wet surface area, and angular orientation of the struts, are shown to be sufficient to predict the functional performance for acoustic absorption coefficient, thermal conductivity, and mechanical Young's modulus. A material property index defined as a weighted sum of normalized functional quantities is used to evaluate the multifunctional performance of the unit cell candidates. It is found that for equal weights assigned to each functional quantity, the combined modulus, thermal conductivity, and sound absorption performance are better with body-centered cubic and A15 surface-based unit cells. For applications involving heat transfer by convection, flow is an additional consideration independent of unit cell geometry. Therefore, an additional non-geometric thermal-fluidic index is defined using Nusselt number and friction factor, which needs computational modeling. The effectiveness of the proposed direct geometry-based selection of periodic cellular structures for multifunctional applications is demonstrated for a combined thermal-acoustics (noise-reducing heat sink) application. Among the considered unit cells, higher porosity octet configuration shows better thermal-acoustic performance for the noise-reducing heat sink application.