Identification of the Piezoelectric Properties of Materials From Impulsive Tests on Cantilever Harvesters

Abstract

Abstract There are many promising applications of vibration energy harvesting based on piezoelectric materials, but some efficient piezoelectric materials e.g. PZT being used inside MFCs include Pb and other elements that are harmful for the environment. Hence, there is a great research effort to develop new eco-friendly piezoelectric materials. In order to make the best use of these materials, a complete characterization of their piezoelectric and mechanical properties is needed. In this paper an alternative identification methodology for the characterization of piezoelectric materials is proposed. A layer of piezoelectric material is bonded to a structural layer making up a cantilever harvester that is excited with impulsive forces. The identification is carried out in the frequency domain, because on the one hand the impact force generates a significant excitation in a wide frequency band and on other hand the cantilever harvester is characterized by a well-distinct resonance peak. The measured frequency response function is fitted with a mathematical model that includes the unknown parameters of the material, which are reconstructed by using an optimization process. In the paper the proposed method is validated identifying the properties of well-known harvesters. Finally, piezoelectric properties obtained by applying an impulsive excitation are compared with those obtained by applying a harmonic excitation generated by a shaker.