Surface strain sensing with polymer piezoelectric film

Abstract A sensing technique for surface strain distributions of a structural component using piezoelectric polymer films is demonstrated. A piezoelectric polymer (polyvinylidene fluoride, PVDF) film is mounted onto the structure surface, and the electric potential induced by the surface deformation is measured with the aid of a non-contact electrostatic voltmeter. The measured potentials are converted into surface strain components using a theoretical formula derived on the basis of linear piezoelectricity. The validity and accuracy of the procedure are illustrated for (i) a plate with a penetrating circular hole and (ii) a plate with a non-penetrating slit-like groove on the back-surface, under in-plane compressive loading. Also, an alternative method for visualization of surface strain patterns using electrically charged powders is demonstrated for plates with back-surface defects.