Wave Control via Phononic Crystals with Adaptively Relaxed Cell Symmetry

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The objective of this award is to introduce a family of crystal-like metamaterials with adaptively relaxed cell symmetry (ARCS) and demonstrate their applicability as tunable acoustic manipulators. The virtue of ARCS crystals lies in their ability to operate in relatively low-frequency regimes, where the performance of wave management methodologies relying exclusively on phononic bandgaps is compromised. The investigation of the ARCS concept will be conducted using a prototype honeycomb with a periodic population of beam resonators instrumented with patches of piezoelectric material. The cell symmetry is relaxed through the modulation of the local effective stiffness of a selected cluster of resonators, which results in the establishment of a non uniform distribution of effective mechanical properties in the medium. The property tuning is enforced through the activation of appropriate sequences of piezoelectric elements of the activation cluster, according to the desired degree of symmetry relaxation. The investigation will be verified by a set of experiments performed using a 3D scanning laser vibrometer. If successful, this research will provide a strategy to achieve versatile acoustic control devices that are immune to some major drawbacks that affect metamaterials based approaches, such as passivity and drastic frequency limitations. The technological applications that would greatly benefit from the ARCS concept include isolation systems, mechanical filters and directional actuators and sensors. The methodology for laser-enabled wave reconstruction that will be specifically developed for this work will provide new general protocols for the experimental characterization of synthetic structural materials at large. This work will open new avenues for research in energy harvesting, towards the design of fully autonomous wave control devices. It will also provide a platform and implement a plan to realize partnerships with local middle and high schools for thematic projects aimed at promoting science and engineering among children and teenagers.