Acoustic absorption properties of granular and 3D printed aerogels

Abstract

Aerogel is a diverse class of nano-porous ultralight solid material. This research examines the acoustic properties of aerogel-based structures and evaluates their suitability for aircraft noise-reduction applications. This thesis characterizes the acoustic absorption properties of two types of aerogel: granular aerogel and 3D-printed structures. In the case of the granular aerogel, we experimentally analyze the granule size distribution for four commercially available aerogels. Subsequently, we experimentally examine the effects of the granule size and sample thickness on sound absorption using the impedance tube. The maximum absorption coefficient for Lumira aerogels (largest tested granule) was found to be 0.99 for 2-inch sample, 0.96 for 1-inch sample, and 0.86 for 0.5-inch sample. We also provide a computational predictive acoustic model for each granule type using FOAM-X software. The second type of aerogel, 3D-printed structures, can be constructed with controlled porosities. In addition, we analyze the effect of the manufacturing process on the acoustic properties. The maximum absorption coefficient increased by 2% for smaller diameter samples when increasing the thickness from 0.5 to 1 inch. While for larger diameter samples, the maximum absorption coefficient increased by 13% when increasing the thickness from 0.5 to 1 inch.