Design of Additively Manufactured Metamaterial for Cabin Noise and Vibrations Reduction

In the last decade many researchers have studied new types of acoustic insulating materials, the acoustic metamaterials. These materials allow to tailor and manipulate the acoustic wave properties, enhancing performances and lowering weight and size of the acoustic insulating solution. In addition, their role as core materials in sandwich panels is of great interest to reduce noise and vibrations inside aircraft cabins, allowing to reach a high transmission loss at low frequencies (e.g. below 1000 Hz), with a consequent positive impact on passengers’ comfort. The high performances of acoustic metamaterials can be enhanced thanks to the new additive manufacturing techniques capable to produce complex geometries, which would be difficult to obtain with the conventional production techniques. The aim of this work is to study, produce and finally redesign a literature case study, in order to adapt it to the typical low frequency acoustic waves of the aeronautical field. We focus on the production quality in order to reproduce the geometrical characteristics of the metamaterial, that influence the acoustic behaviour. The acoustic properties of this unconventional material are studied, through finite element method (FEM) numerical analyses. In this work, the metamaterial geometry is redesigned and then additively manufactured by means of Fused Deposition Modelling. Moreover, the additive baseline material is acoustically characterized. The metamaterial plate was produced with an FDM additive manufacturing system (Fortus 250mc) using an Acrylonitrile Butadiene Styrene (ABS Plus p430) material. The vibration analysis was carried out with the MUL2 software, based on the Carrera Unified Formulation (CUF).