Structural Health Monitoring of Cracked Aircraft Panels Repaired with Bonded Patches Using Fiber Bragg Grating Sensors
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Structural Health Monitoring of Cracked Aircraft Panels Repaired with Bonded Patches Using Fiber Bragg Grating Sensors Hideki Sekine & Shin-Etsu Fujimoto & Tomonaga Okabe & Nobuo Takeda & Toshimitsu Yokobori, Jr.
Received: 26 January 2006 / Accepted: 4 April 2006 # Springer Science + Business Media B.V. 2006
Abstract Structural health monitoring of cracked aircraft panels repaired with bonded patches for extending the service life of aging aircraft has received wide attention. In this paper, the identification of the locations and shapes of fatigue crack and disbond fronts in aircraft panels repaired with double-sided bonded patches using fiber Bragg grating (FBG) sensors is studied. The identification is performed by minimizing the difference between the detected and calculated reflection spectra of FBG sensors at multiple positions on the free surface of patches. The validity and effectiveness of the identification in practical use is verified by comparing the identification results with the exact ones. Key words patch repair . cracked aircraft panel . identification of crack and disbond fronts . reflection spectrum of FBG sensor . improved tunneling method . structural health monitoring
1. Introduction Repair of cracked aircraft panels is necessary to extend the service life of aging aircraft which contain many fatigue cracks resulting from their long service. Repair
H. Sekine (*) : S.-E. Fujimoto : T. Okabe Aerospace Engineering, Tohoku University, 6-6-01 Aoba-yama, Aoba-ku, Sendai 980-8579, Japan e-mail: [email protected] N. Takeda Graduate School of Frontier Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan T. Yokobori Nanomechanics, Tohoku University, 6-6-01 Aoba-yama, Aoba-ku, Sendai 980-8579, Japan
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Appl Compos Mater (2006) 13: 87–98
using bonded fiber-reinforced polymer (FRP) composite patches is recognized to be efficient and cost-effective [1] and has been successfully implemented [2, 3]. In recent years, structural health monitoring of cracked aircraft panels repaired with bonded FRP composite patches has received wide attention. Baker [4] suggested that a smart patch by which in situ structural health monitoring is performed may be necessary to alleviate certification concerns. Chiu et al. [5] reported the possible use of surface-mounted piezoceramics to detect a disbond of FRP composite patch. The use of optical fiber sensors to monitor crack and disbond propagation beneath a repair was also reported in [6–8]. However, these studies are limited to demonstrating qualitatively the possibility of the structural health monitoring. The authors [9, 10] examined a method for identifying the locations and shapes of crack and disbond fronts in repaired aircraft panels, and verified numerically the validity of the identification method. In order to accomplish a high level of safety of the repaired aircraft panels, it is needed to realize accurate structural health monitoring systems. In this paper, the identification of the locations and shapes of fatigue c
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