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Proceedings Paper

Evaluation of debonding progress in composite bonded structures by ultrasonic wave sensing with fiber Bragg grating sensors
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Paper Abstract

The authors are constructing a damage detection system using ultrasonic waves. In this system, a piezo-ceramic actuator generates ultrasonic waves in a carbon fiber reinforced plastic (CFRP) laminate. After the waves propagate in the laminate, transmitted waves are received by a fiber Bragg grating (FBG) sensor using a newly developed high-speed optical wavelength interrogation system. In this research, this system was applied to the evaluation of debonding progress in CFRP bonded structures. At first, small-diameter FBG sensors, whose cladding diameter is about 1/3 of common optical fibers, were embedded in an adhesive layer of a double-lap type coupon specimen consisting of CFRP quasi-isotropic laminates, and the ultrasonic wave was propagated through the debonded region. After that, the wavelet transform was applied to the received waveforms and the results showed clear difference depending on the debonding length. Hence, a new damage index was proposed, which could be obtained from the difference in the distribution of the wavelet transform coefficient. As a result, the damage index increased with an increase in the debonded area. Furthermore this system was applied to the skin/stringer structural element of airplanes made of CFRP laminates. Both of the waves received by a bonded FBG and by an embedded FBG changed sensitively to the debonding progress. Also, the damage index could evaluate the length of the debonding between the skin and the stringer.

Paper Details

Date Published: 16 March 2006
PDF: 11 pages
Proc. SPIE 6179, Advanced Sensor Technologies for Nondestructive Evaluation and Structural Health Monitoring II, 61790G (16 March 2006); doi: 10.1117/12.657510
Show Author Affiliations
Yoji Okabe, The Univ. of Tokyo (Japan)
Junichiro Kuwahara, The Univ. of Tokyo (Japan)
Nobuo Takeda, The Univ. of Tokyo (Japan)
Toshimichi Ogisu, Fuji Heavy Industries, Ltd. (Japan)
Seiji Kojima, Hitachi Cable, Ltd. (Japan)
Shinji Komatsuzaki, Hitachi Cable, Ltd. (Japan)

Published in SPIE Proceedings Vol. 6179:
Advanced Sensor Technologies for Nondestructive Evaluation and Structural Health Monitoring II
Norbert Meyendorf; George Y. Baaklini; Bernd Michel, Editor(s)

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