Acoustical properties of spinodoid porous structures

Abstract

Recently, Kumar et al. [1] have proposed a new class of non-periodic cellular structures called spinodoid (spinodal-like) metamaterials. Spinodal decomposition is a diffusion-driven phase transformation mechanism by which a multiphase solution separates into distinct phases, separated by surfaces with smooth, non-intersecting, and non-periodic topologies. Modifying the classical linear Cahn-Hillard equation—which describes this spinodal decomposition process—by biasing the sampled phase field in a controlled manner, Kumar et al. have provided a numerically efficient method for designing spinodal-like structures. Here, we use this method to generate porous structures with spinodoid topologies and investigate their acoustical properties. The designed spinodoid structures are fabricated using an additive manufacturing process and experimentally studied using a normal incidence impedance tube setup. We investigate the effect of various topological parameters on the acoustical properties, including the effects of through-thickness gradients with finite transition layers. Our results show that the sound absorption and transmission loss properties of such structures can be conveniently altered by altering their cellular anisotropy, making them a suitable candidate for multifunctional applications that require simultaneous high stiffness, high sound absorption performance. [1] S. Kumar, S. Tan, L., Zheng, and D. M. Kochmann, “Inverse-designed spinodoid metamaterials,” npj Comput. Mater. 6(1), 1–10 (2020).