Structural Health Monitoring for Composite Pressure Vessels Using Fiber Optic Sensors

Paper number

IAC-05-C2.4.10

Author

Dr. Tadahito Mizutani, University of Tokyo, Japan

Year

2005

Abstract

Composite pressure vessels are widely used for cryogenic fuel tanks, solid rocket boosters, and recently hydrogen tanks for fuel cell vehicles. Although demand for composite structures rapidly increase due to the advantages in weight, there are few effective assessment techniques to enable the quality control and guarantee the durability. In particular, the microscopic damage detection technology is required because damages such as crack, debonding, and delamination can lead to the critical failure. Among many non-destructive evaluation (NDE) methods for composite structures, optical fibers sensors are especially attractive due to the high sensitivity, the lightweight, and the small size.
Fiber Bragg gratings (FBG) are fabricated in optical fibers by exposing their core to a periodic ultraviolet (UV) pattern and can be designed to cause deflection of light at a specific wavelength, the Bragg wavelength. The refractive index associated with the Bragg wavelength changes due to strain or temperature changes, therefore FBGs are frequently used as strain sensors. Moreover, FBGs have the potential to detect invisible microscopic damages in the composite structures.
This paper presents a real-time strain measurement of a composite LH2 tank in flight experiments of a reusable rocket using the FBGs. This tank, which consists of CFRP and aluminum liner, is fabricated by the filament winding (FW) method and mounted on the reusable rocket. An onboard FBG demodulator was developed in order to be mounted on the rocket. During the flight experiments, the output of the onboard FBG demodulator was continuously monitored via telemetry system. The results of the measurements showed the structural integrity of the tank during the launch operations. Furthermore crack detection in a composite FW tank was attempted using embedded FBGs in order to enhance the structural health monitoring system.

Abstract document

IAC-05-C2.4.10.pdf

Manuscript document

IAC-05-C2.4.10.pdf (🔒 authorized access only).

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