Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
INFLUENCE OF GEOMETRIC PARAMETERS ON THE PIEZOELECTRIC RESPONSE OF THIN PVDF FILMS EXCITED BY LONGITUDINAL MECHANICAL STRESS WAVES
Submission Author:
Luiz Marchezini , MG
Co-Authors:
Luiz Marchezini, Suchilla Garcia Leão, Antonio Avila, Antônio Maia
Presenter: Luiz Marchezini
doi://10.26678/ABCM.COBEM2021.COB2021-0396
Abstract
Films made of a piezoelectric polymer known as polyvinylidene difluoride (PVDF), when coated with silver ink, constitute sensors that can detect and measure in-plane stress waves in structures. These films can be elaborated in different geometrical dimensions, and the final film shape can influence the sensor sensibility and frequency response. The objective of this article is to evaluate the influence of geometrical dimensions of PVDF film sensors on its electrical response when attached to a thin bar exposed to in-plane sinusoidal stress waves. To develop this analysis, a mathematical model was used to simulate the mechanical excitation, the piezoelectric response of the sensor, the relation between the excitation frequency and output electrical impedance, and its impact over the signal obtained using typical electrical measurement equipment like an oscilloscope or voltmeter. Preliminary results showed that the geometrical dimensions and deposition pattern have a great impact on the sensor sensibility and behavior over the frequency spectrum. Evaluating a rectangular sensor shape, it was observed that, due to the stress averaging effect, the sensor’s highest response to mechanical excitations was obtained when its length was minimized and its thickness maximized. Moreover, when the wavelength of the longitudinal mechanical excitation is equal to the sensor length or one of its multiples, the sensor sensibility to this stimulus is completely null. Beyond that, considering the electrical impedance seen by the measurement equipment, a sensor with minimized length and width presents high electrical impedance, especially when the focus of the study is related to low-frequency mechanical excitations. The attenuation of the signal amplitude and phase delay over the frequency, when the sensor is directly connected to an oscilloscope or voltmeter, if not considered, can generate incorrect data about the wave amplitude and the physical phenomenon in the study. It is also expected with this work, contribute with technical information to help users better choose the shape of the sensor when interested in monitor in-plane sinusoidal stress waves in structures.
Keywords
mathematical model, Piezoelectric materials, Polymers, Sensors
