Characterizing piezoelectric properties of PVDF film under extreme loadings

Polyvinylidene fluoride (PVDF) as a polymer has been proven to be an effective piezoelectric sensor with advantages of good flexibility, high mechanical strength, and high chemical resistance. Numerous studies have focused on the response of PVDF film at high strain rates, but few on low strain rate response, and the response of PVDF film at different strain rates is unknown. To address these limitations, we examine the piezoelectric properties of PVDF film at extreme high and low loading rates. We design quasi-static compression and dynamic split Hopkinson pressure bar (SHPB) test setups to examine the response of PVDF film. Quasi-static compression test results show that PVDF films have good repeatability and linearity. The charge shift phenomenon is observed at quasi-static loading conditions, and the charge shift rate is found to be related to the gain coefficient of charge amplifier. Next, SHPB tests are performed and results show that PVDF film can well capture the propagation of stress wave. Moreover, it is observed that the PVDF film under high loading rate has a higher failure strength in comparison to that of low loading rate. Finally, based on the measured points by quasi-static compression and SHPB tests, the piezoelectric coefficients of PVDF film under extreme low (on the scale of strain rate of 10⁻² s⁻¹) and extreme high (on the scale of strain rate 10⁵ s⁻¹) loading rates are found to be 30.79 pC/N and 27.72 pC/N, respectively. Note that, the strain rate difference is seven orders of magnitude, the piezoelectric coefficient difference is only 9.97%. We believe our findings can advance the design and application of PVDF films in practical engineering.