Abstract
In this study, a sandwich piezoelectric nano-energy harvester model under compressive axial loading with a core layer fabricated of functionally graded (FG) porous material is presented based on the nonlocal strain gradient theory (NSGT). The von Karman type geometric nonlinearity and the axial loading were considered. The electromechanical governing equations were obtained using Hamilton’s principle. The nonlinear vibration frequencies, root mean square (RMS) voltage output and static buckling were obtained using the Galerkin method. The effects of different types of porous distribution, porosity coefficients, length scale parameters, nonlocal parameters, flexoelectricity, excitation frequencies, lumped mass and axial loads on the natural frequency and voltage output of nanobeams were investigated. Results show that the porous distributions, porosity coefficient of porous materials, the excitation frequencies and the axial load have a large effect on the natural frequency and voltage output of the sandwiched piezoelectric nanobeams. When the NSGT is considered, the critical buckling load depends on the values of the nonlocal parameters and strain gradient constants. In addition, the electromechanical conversion efficiency of the post-buckling process is significantly higher than that of the pre-buckling process. The flexoelectric effect can significantly increase the RMS voltage output of the energy harvester.
Highlights
The nonlinear electromechanical behavior of the piezoelectric energy harvester model of functionally graded (FG) porous sandwich nanobeams under compressive axial loading is investigated based on the nonlocal strain gradient theory (NSGT)
The results show that: The porous distribution, the porosity coefficient of porous materials, the excitation frequencies and the axial load have a large effect on the vibration frequency and voltage output of the sandwiched piezoelectric nanobeams
The axial load and excitation frequency have an effect on the vibration amplitude of the beam
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Chen and Yan [13] proposed a nonlinear electromechanical model of an energy harvester based on an axial pre-loaded piezoelectric beam, and combined the flexoelectric effect, which can be operated in pre-buckling (monostable) and post-buckling (bistable) configurations. A nonlinear and axial load are considered while analyzing the vibration and bending properties of the sandwich piezoelectric nanobeam. Zeng et al [18] studied the vibration of piezoelectric sandwich nanobeams based on the theory of nonlocal strain gradients and discussed the flexoelectric effect in detail. In this work, we propose a piezoelectric and flexoelectric energy harvester based on the NSGT for FG porous material sandwich nanobeams under axial compressive loading. An energy harvester model sandwich piezoelectric beam composed of FG porous material was developed, in which the FG layer is considered with three porosities.
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