Buckling behavior monitoring of a composite wing box using multiplexed and multi-channeled built-in fiber Bragg grating strain sensors

Abstract Advanced composites are being extensively used for aerospace structures due to their high stiffness–weight and strength–weight ratios. A built-in structural diagnostic system is being developed to continuously monitor the integrity and reliability of the composite structures. Such structures are substantially large, and hence require a large number of sensors. The fiber Bragg grating (FBG) sensor system is a useful tool for health monitoring of such a large structure because it has multiplexing and multi-channeling capabilities. In this paper, an FBG strain sensing system using a wavelength-swept fiber laser (WSFL) was applied for the realization of a smart composite wing box. This system was connected with 24 FBGs, which were embedded into the structural components of the single wing cell. The wing box was tested under bending load, which simulated the lift-induced bending of an airplane wing. Three fiber optic sensor lines were embedded into the top skin and one fiber optic sensor line was embedded into the front spar of the wing box. Experimental results were discussed in comparison with finite element analysis result. All strain data were visualized in real time under the scheme of passive in-situ diagnostics.