Vibration and energy harvesting performance of a piezoelectric phononic crystal beam

Phononic crystal could be used in the vibration energy harvesting devices as its capacity to modulate elastic wave propagation. This paper presents a piezoelectric phononic crystal cantilever beam with periodic variable thicknesses for vibration energy harvesting. The transfer matrix method (TMM) is introduced to analyze the natural frequencies and the band structure of the phononic crystal beam. The influences of structural parameters, such as thicknesses-ratio and lengths-ratio, on the natural frequencies and first band gap of the beam are investigated in detail. The results of first two band gap ranges obtained via the TMM are validated by means of the finite element method (FEM) simulation. Moreover, the electromechanical coupling responses of the phononic crystal beam are explored by using the FEM simulation. The results demonstrate that the piezoelectric phononic crystal beam has more efficient voltage output in the first band gap comparing with the uniform piezoelectric cantilever beam. In conclusion, the proposed piezoelectric phononic crystal beam can extend the bandwidth of the energy harvester in low-frequency vibrations.