Experimental investigation of acoustic absorption of additively manufactured spinodoid metamaterials

Abstract

Porous media have gained attention as a potential replacement for conventional acoustic liners in mitigating aircraft engine noise due to their superior broadband attenuation compared to honeycomb sandwich panels. Among these porous media, the spinodoid metamaterial stands out as a promising candidate. The spinodoid metamaterial is based on spinodal decomposition, a diffusion process in which a high-energy mixture splits into two phases to reduce the overall system energy. Previous investigations have explored the versatile stiffness properties of these materials, highlighting their potential for multifunctional applications, including acoustic liners. This thesis focuses on the experimental study of the acoustic properties of spinodoid materials. Gaussian Random Fields were employed to generate models, offering an alternative to the computationally expensive Cahn-Hillard equation. Additive manufacturing techniques were utilized to fabricate the samples, which were then subjected to experimental testing using a normal incidence impedance tube to measure their acoustic absorption coefficient. A microscopy analysis was conducted to assess any print defects resulting from the manufacturing process. The findings reveal intriguing acoustic performances among the various spinodoid types, indicating their potential for optimization in specific applications, such as acoustic liners for aircraft engines. Overall, this thesis contributes to the understanding of spinodoid materials and their acoustic properties through experimental investigations. The use of Gaussian Random Fields in generating models offers computational efficiency, while additive manufacturing enables the fabrication of complex structures. The results shed light on the acoustic behavior of spinodoid materials, paving the way for their further development and optimization. The potential multifunctionality of these materials, combined with their broadband attenuation characteristics, positions them as promising candidates for reducing noise pollution in aircraft engines.