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Proceedings Paper

Effect of gauge length on embedded fibre Bragg grating sensor response in woven fibre composites
Author(s): Claire Davis; Andrew Philips; Patrick Norman; Nik Rajic
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Paper Abstract

Conventional non-destructive inspection approaches can be costly, require physical access to the subject and some of the established inspection methods are more difficult to implement on polymer composite materials. This has driven a growing interest in the use of embedded sensors. The physical form of optical fibres means they are well suited to embedment in fibre reinforced composites however there are technical challenges associated with their use.

The non-uniform geometry of woven fabric composite materials can induce localised macro bending in embedded optical fibre Bragg grating (FBG) sensors when they are compacted between layers during the lay-up process. This leads to a non-uniform strain profile along the optical fibres which can limit the efficacy of conventional peak tracking algorithms for demodulating strain.

This paper investigates the effect of gauge length on sensor response for FBGs of different length embedded in a woven glass fibre reinforced composite coupon. The experimentally measured FBG reflection spectra were compared to model predictions for the unloaded state assuming an FBG bend radius of similar dimensions to the weft of the fabric. Through thickness fibre optic strains under four point loading conditions were compared to side-imaged thermoelastic response measurements. The results show that the ratio of the gauge length to the curvature radius of the macro bending is critical with the optimal gauge length being a compromise between FBG reflectivity and sensor response.

Paper Details

Date Published: 12 April 2017
PDF: 8 pages
Proc. SPIE 10168, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2017, 101681V (12 April 2017); doi: 10.1117/12.2261775
Show Author Affiliations
Claire Davis, Defence Science and Technology Group (Australia)
Andrew Philips, Defence Science and Technology Group (Australia)
Patrick Norman, Defence Science and Technology Group (Australia)
Nik Rajic, Defence Science and Technology Group (Australia)

Published in SPIE Proceedings Vol. 10168:
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2017
Jerome P. Lynch, Editor(s)

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