Time domain and frequency domain analysis of functionally graded piezoelectric harvesters subjected to random vibration: Finite element modeling

Functionally graded piezoelectric (FGP) material removes the brittleness issue of piezoceramics and small coupling coefficient of piezoelectric polymers. They also avoid the stress concentration and consequently crack propagation. This work addresses the finite element modeling of the functionally graded piezoelectric harvesters subjected to random vibrations. The finite element electro-mechanical governing equations of FGP beam are derived by using the generalized Hamilton's principle under the assumptions of Euler-Bernoulli beam theory. The material properties of the beam are assumed to be varied in the thickness direction following a simple power law distribution. The random base excitation of FGP harvester is assumed to be the Gaussian white noise signal. Both time domain and frequency domain analysis are presented in this work. In the numerical analysis presents the effects of electrical load resistance value, the volume fraction of the piezoelectric material and the PSD level of base acceleration on the expected power output of the piezoelectric harvester are investigated. Numerical results show that a functionally graded reinforcement has a significant influence on the output voltage and the harvested power of the beams. Moreover, the output power increases linearly by increasing PSD level of base acceleration. The results also confirm that time domain and frequency domain analysis results are in good agreement with each other. (C) 2015 Elsevier Ltd. All rights reserved.