Applications of composite materials in aerospace structures is increasing due to the outstanding properties, however, monitoring such composite structures exposed to harsh environments is still a posing issue. Low Earth orbit space structures are exposed to property degradation and damage from high-degree vacuum, ultraviolet radiation, thermal cycling, and atomic oxygen attack which are detrimental to composite materials. In this study, FBG sensors for embedding in CFRP composite plates in different thickness locations to provide health and damage monitoring of the material exposed to such environments regarding the overall health of the material with a focus on the exposed surface are explored in comparison to conventional FBG sensors.
Fiber optic sensors are being spotlighted as the means to monitoring aircraft conditions due to their excellent
characteristics. This paper presents an affordable structural health monitoring system based on a fiber Bragg grating
sensor (FBG) for application in light aircrafts. A total of 24 FBG sensors were installed in the main wing of the test bed
aircraft. In the ground test, the intactness of the installed sensors and device operability were confirmed. During the
flight test, the strain and temperature responses of the wing structure were measured by the on-board low-speed FBG
interrogator. The measured strains were successfully converted into the flight load history through the load calibration
coefficient obtained from the ground calibration test.
Recently, health and usage monitoring systems (HUMS) are being studied to monitor the real-time condition of aircrafts during flight. HUMSs can prevent aircraft accidents and reduce inspection time and cost. Fiber Bragg grating (FBG) sensors are widely used for aircraft HUMSs with many advantages such as light weight, small size, easy-multiplexing, and EMI immunity. However, commercial FBG interrogators are too expensive to apply for small aircrafts. Generally the cost of conventional FBG interrogators is over $20,000. Therefore, cost-effective FBG interrogation systems need to be developed for small aircraft HUMSs. In this study, cost-effective low speed FBG interrogator was applied to full-scale small aircraft wing structure to examine the operational applicability of the low speed FBG interrogator to the monitoring of small aircrafts. The cost of the developed low speed FBG interrogator was about $10,000, which is an affordable price for a small aircraft. 10 FBG strain sensors and 1 FBG temperature sensor were installed on the surface of the full-scale wing structure. Load was applied to the tip of the wing structure, and the low speed interrogator detected the change in the center wavelength of the FBG sensors at the sampling rate of 10Hz. To assess the applicability of the low-cost FBG interrogator to full-scale small aircraft wing structure, a temperature-compensated strain measurement algorithm was verified experimentally under various loading conditions of the wing structure with temperature variations.
Optical fibers can be used as promising sensors in smart structures due to their novel characteristics. This paper presents
a wavelength division multiplexing (WDM) technique in order to improve the application capacity of single reflective
grating based fiber optic sensors to monitor large industrial structures at multiple points. The models are appropriate for
the general extrinsic fiber optic sensors such as the grating panel-based fiber optic sensor. The manufactured WDM fiber
optic sensor system was examined in order to demonstrate the feasibility for two parameter detections at two points using
mirror mounted grating based fiber optic sensor.