Influence of friction on piezoelectric sensors

Piezoelectric sensors are usually made of a sensing element compressed between two plates. Therefore, the applied point/distributed load is transferred through these plates to the piezoelectric sensing element. In this sandwich configuration, surface friction has an inevitable and significant impact on the resultant output of the sensor. This paper reports on the influence of the friction on the output of piezoelectric sensing element in a sandwich structure. Although the numerical analysis as well as experiments are performed on the piezoelectric Polyvinylidene Fluoride (PVDF) films, the results are applicable to similar structures with other piezoelectric materials. The results show the remarkable contribution of the friction induced component in the total output for both uniaxial and biaxial PVDF films. The outcome can be used for the optimization of sensor manufacturing processes. In addition, results suggest an alternative new method for the measurement of d33d33, the PVDF piezoelectric coefficient in the thickness direction. Alternately, it is possible to use the proposed method in order to accurately measure friction coefficients, particularly for low friction range, namely μ<0.1μ<0.1.