Improvements in damage detection using modal strain fields measured by digital shearography

In this paper we present a novel approach for damage detection based on discontinuities analysis of experimental modal strain fields. These fields are extracted from the combination of two rotation fields and they are measured using digital shearography with stroboscopic double illumination. The rotation fields of a damaged laminated plate are frozen by the synchronization between the LASER illumination and the modal vibration of the object. The quantitative evaluation is performed for each digital shearogram using a time modulation technique. The evaluation of a delamination damage on composite plates is performed by using dedicate image processing techniques. Finally, a comparative analysis of damage detections using the experimental measurement of rotation and deformation fields and their spatial derivatives is presented