Cellular phononic crystals with piezoelectric shunts for tunable directivity

Phononic crystals (PCs) are periodic media known for their spectral and spatial wave manipulation capabilities, among which we recall their stop-band filtering behavior, due to the formation of phononic bandgaps, and the spatial directivity, i.e., the inherent ability to produce directional wave patterns. In general, the anisotropic wave propagation patterns of PCs are characterized by multiple equipotent directions of wave beaming, a characteristic which prevents the effective de-energization of arbitrarily selected regions of the PC domain. In this work we discuß a few enhancements of the directivity of lattice-like PCs, obtained through the introduction of shunted piezoelectric inclusions. The lattice links of each unit cell are instrumented with piezoelectric patches, each connected to a separate negative capacitance circuit. By properly choosing the shunting parameters for selected subsets of patches, we can generate peculiar anisotropic stiffneß landscapes and reconfigure the elastic wave patterns accordingly.