Mechanical load effects on the electrostrictive strain of P(VDF-TrFE) copolymer and the development of a high-resolution hydrostatic-pressure dilatometer

The high electric field induced strain response and elastic energy density recently observed in the electron irradiated P(VDF-TrFE) copolymer beckons its adoption in transducer applications. Due to its compliant nature however, concern exists over the effect of mechanical stress on the electrically induced strain. This paper investigates the electrostrictive strain-response of the irradiated copolymer in the longitudinal (parallel to the field) direction as a function of hydrostatic pressure and in the transverse direction as a function of tensile stress. The longitudinal strain was characterized via the development of an automated hydrostatic-pressure dilatometer specifically designed for compliant films. Various performance parameters of this bimorph-based strain sensor are analyzed including the noise, resolution and frequency response. The results are compared with similar data from axially stressed samples that corroborate the conclusion that this modified copolymer exhibits a high load capability