Electronic Speckle Pattern Interferometry (ESPI) for impact damages evaluation on CFP

In this work, the application of Electronic Speckle Pattern Interferometry (ESPI) in composites, which are used in the aeronautic field, is presented. Through real-time surface illumination by visible laser (i.e. 532 nm), the ESPI technique allows the non-contact, non-destructive detection of micro-deformations, micro-cracks, residual stress and delaminations. The measurement range and accuracy is related to the light wavelength and the deformation value is measured by half-wavelength multiples. The method records the surface field differential displacement, due to thermal or mechanical strains. A CCD camera records the whole field deformation into images to be processed. By this technique, it is possible to reveal hidden defects and to evaluate the effective delamination area due, for example, to an impact damage.