Simultaneous Damage Detection and Deflection Measurement of Morphing Wing Structures by Fiber Optic Sensing System

Abstract : In this paper we present results of investigation of simultaneous damage detection and deflection measurement of morphing CFRP honeycomb structure by fiber optic sensing system developed in the frame of EU-FP7 project ÒFiber Optic System for Deflection and Damage Detection (FOS3D)î. The system is based on low- and high-coherence interferometry performed as Òall-in-fiberî sensing configuration. Raw signals have been on- and off-line processed by Òarctangî algorithm. Deflection data, expressed as phase angle change of the interferometer, have been simultaneously acquired with the reference data. A linear relationship between the fiber-optic sensing and reference technique is obtained. Slope of the linear fit line of 8 rad/mm denotes sensitivity of this sensor. Noise floor of about ±70µrad/√,Hz determines the lowest measurable wing deflection of about 6µm. Damage events have been simulated by pencil break and hammer impact with- and without damages over the CFRP honeycomb structure. Raw fiber-optic interference and reference acoustic emission sensor signals have been simultaneously acquired. Figure of merit is given as probability of detection (POD) and localization of simulated impact event. All events can be detected and located with a POD of more than 98% within the localization error of around 15 mm.