Development of a 2D DIC Experimental Tool for Piezoelectric Strains Measurements

Piezoelectric materials are used in a wide range of actuation and sensing applications. The characterisation of their non-linear coupled electro-mechanical behaviour is a real challenge due to the heterogeneity of materials, the complexity of boundary conditions, and safety issues related to severe loading conditions (electric field, stress, temperature). In this context, Digital Image Correlation (DIC) is a promising tool for piezoelectric materials characterisation since this non-contact method enables remote full-field measurements of strains. In the present work, a 2D DIC bench has been developed for high resolution displacement measurements. The proposed experimental set up uses the long distance microscope Questar QM100 and a low speed 9 megapixels camera. Since a micrometric speckle is needed, Badger Sotar 20/20 airbrush combined with nano-pigment paints has been used. In a first step, the setup has been characterised in order to identify the optimal speckle size for our application. In a second step, an optical characterization tool has been developed to minimize errors from experimental setup and image acquisition. Based on our studies, the DIC bench was calibrated and measurement noise has been assessed experimentally. For this purpose, a piezoelectric sample was deformed and characterised under a quasi-static electrical loading. From these experimental results, the noise level is estimated and discussed.