Nonlinear analysis of functionally graded flexoelectric nanoscale energy harvesters

Abstract

Due to the strong size-dependent property, flexoelectricity is one of the most advantageous applications of piezoelectricity on the micro/nano scale energy harvesting. However, rare researches have been conducted on energy harvesters composed by functionally graded flexoelectric materials (FGFMs). In this paper, the nonlinear vibration of a FGFMs energy harvesting nanobeam with a concentrated mass located at free end is analyzed theoretically while considering the electromechanical coupling effect induced by strain gradients. By referring to the Galerkin's method, the corresponding equations of the coupled system and the approximated closed-form solutions of the electric and the power output are obtained. In numerical part, the influences of the volume ratio of the material components, the gradient index and the loading resistance on the voltage output and power density are studied in detail. It is found that, for FGFMs energy harvester, the effective voltage output and the power density depend enormously on the material constituents, the gradient index, the scaled size and the loading resistance. And the rationality of our proposed model is verified by the numerical results. Thus, we can conclude that, for the energy harvesting triggered by flexoelectricity, the FGFMs may be a good way for device design owing to its easy generation of large strain gradients.