Design and Characterization of Fiber-Optic Interferometric Sensor for Deflection and Damage Detection of Morphing Wing Structures

Abstract

The paper deals with a non-destructive technique capable for simultaneous damage and deflection detection of aircraft’s morphing wings made as a sandwich structure of CFRP. We proposed a fiber-optic low-coherence interferometry as a sensing platform for deflection and structural health monitoring of aircraft morphing wings in the frame of an EU-FP7 project, named “Fiber Optic System for Deflection and Damage Detection (FOS3D)â€. Fiber-optic sensors (FOS) of different forms are adhesively bonded over the top and down side of the CFRP morphing structure. We performed theoretical and experimental exploration of such a system steaming from the FEM simulation of deformation magnitude in dependence on the inclination angle (±5°) of the morphing tail. Then we calculated the change of the optical path difference (OPD) induced in the FOS in dependence on the inclination angle and found correlation between the OPD of FOS and coherence length of the used superluminiscente diodes (SLD). The CFRP structure and FOS have been simultaneously subjected to the deflection by standard four-point bending test and to damage by “pencil brake testâ€. During loading of the CFRP plate raw interferometric signals have been acquired and then off-line processed by “arctan†algorithm. We determined the most critical parameters of the fiber-optic sensing configuration, which provide information on deflection and damage events raised into the subjected CFRP specimen.