Effect of geometrical defects on the acoustical and transport properties of periodic porous absorbers manufactured using stereolithography

Abstract

Additive manufacturing allows the fabrication of acoustical materials with previously unrealizable micro- and macrostructural complexities. However, the still nascent understanding of various geometrical defects occurring during the additive process remains a barrier to accurately predicting the acoustical behavior of such complex absorbers. In this study, we present the results from our efforts on numerically modeling the absorption behavior of periodic porous absorbers fabricated using the stereolithography (SLA) technique using the hybrid micro-macro multiphysics approach. Specifically, we focus on understanding the role played by the expansion or shrinkage of the solid ligaments during the SLA process on the transport parameters of the final printed samples. First, the periodic absorbers are modeled using COMSOL multiphysics, where the transport properties are derived using the Johnson-Champoux-Allard-Lafarge-Pride (JCALP) semiempirical model. Results from the parametric study guide the design and fabrication of test articles that closely match the initial design requirements. Finally, the fabricated samples are tested using an impedance tube, and the obtained absorption properties are compared to the a priori numerical predictions. Results indicate that accounting for fabrication defects within the numerical modeling schema can provide reliable sound absorption predictions for additively manufactured porous absorbers.