Improving the vibroacoustic performance of metastructures by inclusion of nonlinear local resonators

Abstract

The use of periodicity has become an interesting solution for structural noise and vibration reduction in many engineering applications. Acoustic metamaterials are structures built using such repetitive assemblies of identical elements to explore either Bragg-scattering or internal resonance to control mechanical waves. They present frequency bands in which waves do not freely propagate, named bandgaps, allowing acoustic and vibration attenuation at various frequency ranges. For a given linear time-invariant system, the width and depth of the bandgaps are fixed and may be prone to lose performance if the disturbance or environment properties change. One way of addressing this issue is via active means, which actuate on the system to adjust some parameters to match the desired properties. However, such solutions can be complex, involving the use of transducers, electronics, and software, besides increasing cost and jeopardizing robustness. In this context, nonlinear elements can be used to provide an otherwise linear system with dynamic properties that change concerning the level of excitation, for example. If properly designed and implemented, nonlinear stiffness can result in resonance frequency shits that broaden the attenuation frequency band and better isolate subsystems that could be sensitive to higher excitation levels. Therefore, this project aims to enhance vibro-acoustic performance of metastructures with the inclusion of nonlinear local resonators. To that end, it will develop on the design, modeling, simulation, and experimental validation of nonlinear metastrucutres, from unit-cell to full-system level.