Influence of thermal deformations on sound absorption of three-dimensional printed metamaterials

Abstract

Acoustic metamaterials (AMMs) are designed with complex geometrical shapes to obtain unconventional sound-absorbing performances. As additive manufacturing is particularly suited to print complex structures in a more straightforward and controllable way, AMMs often exploit three-dimensional (3-D) printing techniques. However, when exposed to different temperature conditions, such structures can be affected by geometrical deformations, especially when they are polymer-based. This can cause a mismatch between the experimental data and the expected theoretical performance; therefore, it is important to take thermal effects into account. The present paper investigates the influence of thermal deformations on the sound absorption of three geometries: a coplanar spiral tube, a system with double coiled resonators, and a neck-embedded resonator. Measurements were performed on each 3-D printed specimen in the impedance tube after the samples had been placed in a climate chamber to modify the temperature settings (T = 10–50 °C). Numerical models, validated on the measurements, were employed to quantify the geometrical deformation of AMM structures through a multiphysics approach, highlighting the effects of thermal stress on the acoustic behavior. The main outcomes prove that the frequency shifts of sound absorption peaks depend on temperature configurations and follow exponential regressions, in accordance with previous literature on polymeric materials.

The effect of sound-absorbing walls in the design of cavity- based metamaterials

“…Numerous references with the formulation of innovative structures designs and simulation methods have been published [2][3] [4], while only a few of them cover the fundamentals for the actual sample preparation and measurements. Usually, the prototype samples are manufactured in the 3D printing process and some works on the resulting surface roughness and its influence on the simulated sound absorption coefficient values have been published [5]- [7]. In the current project, we have experienced a great dispersion in the measured and simulated sound absorption values in a prototyped singlecell metamaterial structures, and one of the explanations for this phenomenon was the additional sound absorption of the bare material walls manufactured with 3D printing.…”

Influence of additive manufacturing on acoustic metamaterials performance: a case study

“…For this reason, they were selected in this research to investigate the accuracy of different 3D printing materials and methods in reproducing the expected analytical and numerical results. Specifically, the geometrical model of coiled-up resonators that will be used has already been discussed in previously published papers [11], [14]. In order to assess the analytical results and implement the metamaterial geometry through parametric sweeps, numerical models helped setting up a reference α-value in reference conditions (T = 20 °C) through the commercial software COMSOL Multiphysics [11], [15].…”

“…For these reasons, the present parametric and comparative investigation aims to determine whether, for spiral resonators, there may be an optimal configuration of techniques and materials for AM that can best approximate the designed analytical and numerical result. Firstly, Stinson's analytical model [10] coupled with a numerical analysis using the finite element method (FEM) [11] under measurement-like conditions provided an initial predicted result of the sound absorption coefficient. Secondly, a series of AM techniques (FDM, SLA and Selective Laser Melting, SLM) and 3D printing materials (PLA, PETGg, Resin, flexible resin and stainless Steel) were used to produce the spiral resonator with various 3D printing setups (see Figure 1).…”

A Compact Tunable Broadband Acoustic Metastructure with Continuous Gradient Spiral Channels

“…The membrane-type structure, coiling-up space structure, and Helmholtz-resonatorlike structure have been developed rapidly. [9][10][11][12][13] The strategy of combining porous material with acoustic metastructure to achieve fullband sound absorption has also been adopted by many researchers. [14][15][16] The coiling-up space structure can increase the acoustic transmission path and reduce the thickness in the limited volume by bending and folding the cavity in space.…”

“…The membrane‐type structure, coiling‐up space structure, and Helmholtz‐resonator‐like structure have been developed rapidly. [ 9–13 ] The strategy of combining porous material with acoustic metastructure to achieve full‐band sound absorption has also been adopted by many researchers. [ 14–16 ]…”