A recent technological revolution in the fields of integrated MEMS has finally rendered possible the mechanical integration of active smart materials, electronics and power supply systems for the next generation of smart composite structures. Using a bi-dimensional array of electromechanical transducers, composed by piezo-patches connected to a synthetic negative capacitance, it is possible to modify the dynamics of the underlying structure. In this study, we present an application of the Floquet-Bloch theorem for vibroacoustic power flow optimization, by means of distributed shunted piezoelectric material. In the context of periodically distributed damped 2D mechanical systems, this numerical approach allows one to compute the multi-modal waves dispersion curves into the entire first Brillouin zone. This approach also permits optimization of the piezoelectric shunting electrical impedance, which controls energy diffusion into the proposed semi-active distributed set of cells. Furthermore, we present experimental evidence that proves the effectiveness of the proposed control method. The experiment requires a rectangular metallic plate equipped with seventy-five piezo-patches, controlled independently by electronic circuits. More specifically, the out-of-plane displacements and the averaged kinetic energy of the controlled plate are compared in two different cases (open-circuit and controlled circuit). The resulting data clearly show how this proposed technique is able to damp and selectively reflect the incident waves.
A two-dimensional array of piezoelectric transducer (PZT) shunted on negative capacitance circuit is designed and applied to achieve broadband vibration reduction of a flexible plate over tunable frequency bands. Each surface-bonded patch is connected to a single independent negative capacitance synthetic circuit. A finite element-based design methodology is used to predict and optimize the attenuation properties of the smart structure. The predictions are then experimentally validated by measuring the harmonic response of the plate and evaluating some derived quantity such as the loss factor and the kinetic energy ratio. The validated model is finally used to explore different configurations with the aim of defining some useful design criteria. The results obtained clearly show how the proposed strategy represents a robust and effective solution for the control of vibrations in complex structures.
Research activities in smart materials and structures are very important today and represent a significant potential for technological innovation in mechanics and electronics. The growing interest of our society in the problem of sustainable development motivates a broad research effort for optimizing mechanical structures in order to obtain new functional properties such as noise reduction, comfort enhancement, durability, decreased ecologic impact, etc. In order to realize such a multi-objective design, new methods are now available which allow active transducers and their driving electronics to be directly integrated into otherwise passive structures. This new concept could allow fine control of the material physical behavior to induce new functional properties that do not exist in nature and that cannot be introduced by passive approaches. In this sense, we can speak of "integrated distributed adaptive metacomposites" that merges with the notion of programmable material. Through two different examples dealing with active acoustical impedance and elastodynamical interface, this paper present theoretical tools and validations for designing specific applications of this new technology.
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