Enhancement of elastic wave energy harvesting by utilizing a phononic crystal (PnC) is a hot topic in electroelastic systems. Piezoelectric energy harvesting (PEH) is implemented herein due to attaching a piezoelectric transducer (PZT) disk on a 2D starlike hole-type PnC with a line-defect. Waveguide and energy localization will lead to the amplification of harvestable mechanical energy using the opened complete bandgaps of the PnC. For a given line-defect PnC structure, two geometric parameters (diameter and thickness of the PZT disk) of the PEH device are found to be key factors to influence the energy harvesting performance. Therefore, the finite element method is used to obtain the optimal diameter and thickness of the PZT disk through the design of numerical experiments. Using the two optimal geometric parameters, the electric power amplification ratio of the present PEH device will be 26.7 times over that of the PEH device using a thin plate with the same outer dimensions.

Phononic crystal (PnC) has been proved for its manipulation and amplification of elastic waves. Using this characteristic of PnC to assist energy harvesting has remarkable effect. Generally, defect occurs when unit cell in PnC is replaced by another cell with different geometric or material properties, the output electric power of piezoelectric energy harvesting (PEH) devices will be significantly enhanced. In this study, a cross hole-type PnC-assisted PEH device with a large-size defect is presented by replacing several adjacent multiple cells with other cells. It is found that multiple peak voltages can be created within BG and multimodal energy harvesting can be performed. Compared with the defect mode composed of a small-size defect, energy localization and amplification of the proposed PnC leads to substantially enhancement of harvesting power after tailoring geometric parameters of a PEH device. This work will be expected to design PnC-assisted PEH devices in a reasonable way.

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In this paper, a windmill-like phononic crystal (PC) structure with optimal locally resonant bandgaps (LRBGs) is proposed. By analyzing the variation trend of BGs, three geometric parameters (the side length and height of cuboid scatterer, and the width of elastic beams) are found to be key factors for the determination of BGs. Using response surface methodology (RSM), 3-factor and 7-level experiment are designed to obtain experimental data with the help of finite element simulations. Three relationships (fitting equations) between the three factors and the second BGs terminating frequency, the first BGs bandwidth, and the second BGs bandwidth, are further obtained by fitting the simulation data. Based on the three fitting equations, the optimal LRBGs are finally obtained using a simple optimization method. The proposed windmill-like structure PC is demonstrated to possess an optimal range of BG.

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