PVDF piezoelectric voltage coefficient in situ measurements as a function of applied stress

Direct piezoelectric g(31) voltage coefficient was measured in situ as a function of applied tensile stress for films of polyvinylidene fluoride (PVDF). Measurements were performed under quasi-static conditions with applied strain rates of 0.5-1.5 mm/min for strains up to 12%. Open-circuit voltage was measured with a contact-less electrostatic voltmeter. Obtained results show a strong dependence of the g(31) coefficient of mono-oriented PVDF films on the applied stress, with a maximum value of the coefficient in the transition region between elastic and plastic deformation zones. The effect of sample geometry on the apparent g(31) coefficient is shown and discussed. The anisotropy of the piezoelectric effect is studied by means of g(31) and g(32) measurements. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43248.