SPECKLE INTERFEROMETRIC DAMAGE INVESTIGATION OF FIBER-REINFORCED COMPOSITES

With the aid of the recently reported technique of adding up phase ima ges module 2 pi that correspond to stepwise applied load increments, t he fringe density that can be achieved in electronic speckle pattern i nterferometry (ESPI) has been substantially improved. This technique a lso allows the measurement of much larger deformations than were hithe rto possible with ESPI. The analytical power of the method is demonstr ated in the measurement of high local displacement gradients in carbon fibre-reinforced plastics (CFRPs). In-plane and out-of-plane displace ment field measurements, performed with one single optical instrument, are compared with finite-element models. This paper reports how the t echnique is used to detect and quantify damage in fatigued CFRP lamina tes via its effect on the surface displacement field. Moreover, the me asured displacement fields are used to validate a finite-element damag e model. The correctness of the delamination measurement is verified w ith the aid of ultrasonic C-scan reference results.