An Aircraft Structural Health Monitoring Using Brillouin Scattering Sensing System

Structural health monitoring (SHM) means a system with the ability to detect damage and /or prediction structural life in order to improve reliability and reduce life-cycle cost. In the SHM, optical fiber sensor system is an attractive one for aircrafts SHM, because of its light weight, durability, and enable to be embedded into composite structures. We chose the Brillouin measurement method to detect strain distribution and strain history of structures, in order to monitor structural health. In this paper, we developed a prototype Brillouin optical correlation domain analysis (BOCDA) and carried out three application tests to verify the capability for (SHM). The prototype BOCDA system is able to measure the distribute strain of full-length optical fiber sensor with 50mm of spatial resolution and 2.7Hz sampling for arbitrary point strain. Moreover, we conducted three application tests to evaluate the effectiveness of SHM using the BOCDA system, such as the panel buckling test, the dynamic strain measurement test, and the demonstration flight test. We verify the effectiveness of the BOCDA system for the aircraft SHM, and clarify the necessary development subject for the actual application. INTRODUCTION Recently, an application of the aircraft structural health monitoring (SHM) system is hoped by airline from the demand of low cost aircraft operation. Many researches have been conducted for application of SHM techniques. The SHM technology using an optical fiber sensor is very attractive method for aircraft SHM system because of its lightweight, durability, and to be embedded into composite structures. The Brillouin scattering method, that can measure distributed strain on the full-length optical fiber sensor, is one of the effective methods for large area monitoring. The Brillouin optical time domain reflectometer (BOTDR) is popular method of the distributed optical fiber 1 Mitsubishi Heavy Industries, LTD. Nagoya Aerospace Systems 10, Oye-cho, Minato-ku, Nagoya 455-8515, Japan 2 Mitsubishi Heavy Industries, LTD. Nagasaki R&D Center 5-717-1, Fukahori-machi, Nagasaki 851-0392, Japan 3 R&D and Institute of Metal and Composite for Future Industries 25-2, Toranomon 3-Chome, Minato-ku, Tokyo 105-0001, Japan