Modelling, analysis and experimental validation of vibro-acoustic locally resonant metamaterials including damping, by Lucas Van Belle (KU Leuven)

DENORMS Action’s Workshop “Modelling of high performance acoustic structures Porous media, metamaterials and sonic crystals”, Rome, 24-25th January 2017

Website of DENORMS Action

Programme of the Workshop

Session on New trends in vibroacoustics (i.e. elastic metamaterials and metasurfaces)

Speaker: Lucas Van Belle (KU Leuven)

Abstract:

Over the past decades, increasingly stringent emission regulations have given rise to the use of lightweight materials and designs. Meanwhile, the growing awareness of the health impact of noise and vibrations leads to ever tightening noise and vibration exposure regulations. Apart from legal considerations, growing customer expectations require products to exhibit favorable noise, vibration and harshness (NVH) behavior. Since the NVH performance of conventional panels and structures is mainly driven by their mass, often heavy or bulky constructions are required, especially in the low frequency regime. Since this conflicts with the trend towards lightweight design, novel low mass and compact volume NVH solutions are sought to face the challenge of combining both NVH and lightweight design requirements. Recently, vibro-acoustic locally resonant metamaterials have come to the fore in noise and vibration control engineering as a possible novel NVH solution. These metamaterials show great potential due to their superior noise and vibration attenuation performance in targeted and tunable frequency ranges, referred to as stop bands, which can be obtained by adding or embedding elastic resonant structures to an elastic host structure on a subwavelength scale. In view of extending their applicability, these locally resonant metamaterials should become exploitable in a broader frequency range. It has been shown in previous research that the presence of damping has an important influence on the vibro-acoustic performance of these materials, broadening the frequency range of attenuation at the expense of peak attenuation. Understanding and including the effects of damping is thus necessary to gain insight into and more accurately predict the performance of these locally resonant metamaterials. Classically, these often periodic structures are analysed using a unit cell modelling approach to predict the wave propagation and thus stop band behavior in infinite periodic structures, discarding damping. Consequently, unit cell models have been developed including damping, to analyse the complex dispersion curves for these locally resonant metamaterials. In this presentation the effect of damping in both resonator and host structure on the dispersion curves is studied. The obtained dispersion curves are validated through an experimental dispersion curve measurement based on an extended Inhomogeneous Wave Correlation method using Scanning Laser Doppler Vibrometry. For the validation, an 0.6x0.6m aluminum panel with glued acrylic resonant structures was manufactured to form a metamaterial plate, showing excellent agreement between numerical predictions and experimental measurements.