Measurement of static strain distribution using piezoelectric polymer film(principle and application to a holed plate)

The objective of the present study is to exploit the feasibility of piezoel ectric polymer film sensors to evaluate in-plane static strain distribution s of structural components. In contrast to ordinary use of piezoelectric fi lms as strain and strain-rate sensors detecting electric charges or current s in a closed circuit, the proposed strategy consists of directly measuring the distribution of electric potentials induced in the piezoelectric film mounted on the surface of a deforming structural component. Strain distribu tions are determined from the measured potentials taking into account the p iezoelectric constitutive law of the film material. As an illustrative exam ple, thin films of polarized polyvinylidene fluoride (PVDF) are mounted on a holed elastic plate subjected to in-plane loading, and the induced potent ial distributions are measured on the film surface by an electrostatic volt meter. It is demonstrated that the determined strain distributions are in f air conformity with those predicted by the theory of linear elasticity.