An active viscoelastic metamaterial for isolation applications

Abstract

Metamaterials are of interest due to their ability to produce novel acoustic behaviour beyond that seen in naturally occurring media. Of particular interest is the appearance of band gaps which lead to very high levels of attenuation within narrow frequency ranges. Resonant elements within metamaterials allow band gaps to form within the long wavelength limit at low frequencies where traditional passive isolation solutions suffer poor performance. Hence metamaterials may provide a path to high performance, low frequency isolation. Two metamaterials are presented here. An acoustic material consisting of an array of split hollow spheres is developed, and its performance is validated experimentally. The application of an acoustic/mechanical analogy allows the development of an elastodynamic metamaterial that could be employed as a high performance vibration isolator at low frequencies. A prototype isolator is manufactured, and its performance is measured. The passively occurring band gap is enhanced using an active control architecture. The use of the active control system in conjunction with the natural passive behaviour of the metamaterial enables high levels of isolation across a broad frequency range. An eventual goal of the work is to produce such materials on a small scale, and as such the metamaterials developed are designed for, and produced using, additive layer manufacturing techniques.