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Proceedings Paper

Monitoring of crack growth beneath a bonded repair using Bragg gratings
Author(s): Iain A. McKenzie; Rhys Jones; W. K. Chiu; D. Booth; S. Galea
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Paper Abstract

In the aircraft industry the use of externally bonded composite repairs has become an accepted way of repairing fatigue, or corrosion, damaged metallic structural components. Optical fibers offer a means of monitoring the load transfer process in these repairs, and can therefore be used to provide an indication of the integrity of the repair. This paper describes the use of an array of fiber Bragg grating strain sensors (FBGs) for the in-situ monitoring of bonded repairs to aircraft structures and, in particular, the monitoring of crack propagation beneath a repair. In this work the FBGs have been multiplexed using a combination of wavelength and spatial techniques employing a tunable Fabry-Perot filer to track individual gratings. The multiplexed FBGs were then surface mounted on a Boron-Epoxy unidirectional composite patch bonded to an aluminium component. The sensors were located so as to monitor the changing stress field associated with the propagation of a crack beneath the patch. The ability of relating experimental results to sensor readings is then confirmed using both a thermo-elastic scan of the patch and 3D finite element analysis. Additionally, the relative merits of surface bonding verses embedding sensors are discussed, and a standardized embedding procedure for fiber optic sensor in Boron-Epoxy patches is described.

Paper Details

Date Published: 14 November 1997
PDF: 12 pages
Proc. SPIE 3242, Smart Electronics and MEMS, (14 November 1997);
Show Author Affiliations
Iain A. McKenzie, Monash Univ. (Australia)
Rhys Jones, Monash Univ. (Australia)
W. K. Chiu, Monash Univ. (Australia)
D. Booth, Victoria Univ. of Technology (Australia)
S. Galea, Defence Science and Technology Organisation (Australia)

Published in SPIE Proceedings Vol. 3242:
Smart Electronics and MEMS
Alex Hariz; Vijay K. Varadan; Olaf Reinhold, Editor(s)

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