Bending piezoelectricity in monomorph polymer films

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Abstract
Studies with laser‐induced pressure pulses show the existence of a piezoelectric monomorph polarization in 22–25‐μm‐thick PVDF films after irradiation with a 30‐kV electron beam. The bending piezoelectric stress constant β31 and the tensile piezoelectric strain constant d31 were determined for such monomorph samples. Both β31 and d31 increase with increasing irradiation time and a linear relation between them is found. The highest values of β31 and d31 achieved are 90 nC/m and 3 pC/N, respectively. A theory is presented for a film with a step‐shaped distribution of polarization along the thickness. A bending piezoelectric strain constant f31 is defined which relates the electric displacement to the stress gradient along the thickness. It is concluded that β31 is determined by the distribution of d31 and f31.