Open Access

ARTICLE

Brillouin Spectral Response Depending on Strain Non-Uniformity within Centimeter Spatial Resolution and its Application to Internal Damage Detection in Large-Scale Composite Structures

Shu Minakuchi¹, Tadahito Mizutani¹, Haruka Tsukamoto², Mayuko Nishio², Yoji Okabe³, Nobuo Takeda¹

1 Department of Advanced Energy, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8561, Japan
2 Department of Aeronautics and Astronautics, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
3 Department of Mechanical and Biofunctional Systems, Institute of Industrial Science, The University of Tokyo, 46-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

Structural Durability & Health Monitoring 2008, 4(4), 199-220. https://doi.org/10.3970/sdhm.2008.004.199

Abstract

The authors propose a technique to detect centimeter internal damages in large-scale composite structures, using an optical fiber network running throughout the structure. A Brillouin-based distributed strain sensing system with centimeter-order spatial resolution (pre-pump pulse Brillouin optical time domain analysis (PPP-BOTDA)) was utilized to detect residual non-uniform strain in the damaged area. First, Brillouin spectral response depending on the strain profile within the spatial resolution was revealed. The spectral response depending on strain non-uniformity was experimentally quantified with consideration of the general characteristics of the Brillouin gain spectrum. Then, the damage detection procedure was proposed, based on the spectral response. Finally, impact damage detection of a composite sandwich structure was numerically conducted to illustrate the effectiveness of the proposed technique. The developed system is quite useful in a first inspection of large-scale composite structures in aerospace applications.

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