We report a new class of tunable and switchable acoustic metamaterials comprising resonating units dispersed into an elastic matrix. Each resonator consists of a metallic core connected to the elastomeric matrix through elastic beams, whose buckling is intentionally exploited as a novel and effective approach to control the propagation of elastic waves. We first use numerical analysis to show the evolution of the locally resonant band gap, fully accounting for the effect of nonlinear pre-deformation. Then, we experimentally measure the transmission of vibrations as a function of the applied loading in a finite-size sample and find excellent agreement with our numerical predictions. The proposed concept expands the ability of existing acoustic metamaterials by enabling tunability over a wide range of frequencies. Furthermore, we demonstrate that in our system the deformation can be exploited to turn on or off the band gap, opening avenues for the design of adaptive switches.

Silicon edges as one-dimensional waveguides for dispersion-free and supersonic leaky wedge waves Appl. Phys. Lett. 101, 031904 (2012) Surface acoustic wave band gaps in a diamond-based two-dimensional locally resonant phononic crystal for high frequency applications J. Appl. Phys. 111, 014504 (2012) In-plane confinement and waveguiding of surface acoustic waves through line defects in pillars-based phononic crystal AIP Advances 1, 041404 (2011) An acoustic bending waveguide designed by graded sonic crystalsOne of the outstanding challenges in phononic crystals and acoustic metamaterials development is the ability to tune their performance without requiring structural modifications. We report on the experimental demonstration of a tunable acoustic waveguide implemented within a two-dimensional phononic plate. The waveguide is equipped with a periodic array of piezoelectric transducers which are shunted through passive inductive circuits. The resonance characteristics of the shunts lead to strong attenuation and to negative group velocities at frequencies defined by the circuits' inductance. The proposed waveguide illustrates the concept of a controllable acoustic logic port or of an acoustic metamaterial with tunable dispersion characteristics. V C 2012 American Institute of Physics. [http://dx.

In this work, a periodic 4 × 4 lay-out of resistive inductive (RL) shunted piezoelectric transducer (PZT) patches is designed and applied to achieve broadband vibration reduction of a flexible isotropic plate over tunable frequency bands. Each surface-bonded PZT patch is connected to a single independent RL circuit and all shunt circuits are tuned at the same frequency. A finite element-based design methodology is used to predict the attenuation properties of the unit cell that characterize the periodic assembly. The predictions are experimentally validated by measuring the spatial average harmonic response of the plate. Significant broadband attenuation is obtained over frequency bands centered at the resonance frequency of the shunting circuit.

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Periodic arrays of hybrid-shunted piezoelectric actuators are used to suppress vibrations of an aluminum plate over broad frequency bands. Commonly, piezoelectric-shunted networks are used for individual mode control, through tuned, resonant resistive/inductive circuits, and for broadband vibration attenuation, through negative impedance converters. Periodically placed resonant shunts allow for broadband reduction resulting from the attenuation of propagating waves in frequency bands which are defined by the spatial periodicity of the array and by the shunting parameters considered on the circuit. Such attenuation typically occurs at medium–high frequencies, while negative impedance converter networks are effective in reducing the vibration amplitudes of the lower modes of the structure. In this article, the combination of periodic resonant shunts and negative impedance converter networks on the same aluminum panel is studied to verify the possibility of combining the advantages of the two concepts. Both numerical and experimental investigations demonstrate that broadband attenuation is achieved in the mid–high frequency regimes due to the presence of resistive/inductive networks, while the combination with negative impedance converter circuits is responsible for amplitude reduction of the full frequency spectrum. Numerical simulations and frequency response measurements on a plate demonstrate that an attenuation region of about 1000 Hz is achieved with a maximum 8 dB vibration reduction.