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Proceedings Paper

Recovering strain readings from chirping fiber Bragg gratings in composite overwrapped pressure vessels
Author(s): Scott M. Strutner; Frank Pena; Anthony Piazza; Allen R. Parker; W. Lance Richards; Gregory P. Carman
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Paper Abstract

This study reports on signal recovery of optical fiber Bragg gratings embedded in a carbon fiber composite overwrapped pressure vessel's (COPV) structure which have become chirped due to microcracks. COPVs are commonly used for the storage of high pressure liquids and gases. They utilize a thin metal liner to seal in contents, with a composite overwrap to strengthen the vessel with minimal additional mass. A COPV was instrumented with an array of surface mounted and embedded fiber Bragg gratings (FBGs) for structural health monitoring (SHM) via strain sensing of the material. FBGs have been studied as strain sensors for the last couple decades. Many of the embedded FBGs reflected a multi-peak, chirped response which was not able to be interpreted well by the current monitoring algorithm. Literature and this study found that the chirping correlated with microcracks. As loading increases, so does the number of chirped FBGs and microcracks. This study uses optical frequency domain reflectometry (OFDR) to demultiplex the array of FBGs, and then sub- divide individual FBGs. When a FBG is sub-divided using OFDR, the gratings' strain along its length is recovered. The sub-divided chirped FBGs have strain gradients along their length from microcracks. Applying this to all chirped gratings, nearly the entirety of the embedded sensors' readings can be recovered into a series of single peak responses, which show very large local strains throughout the structure. This study reports on this success in recovering embedded FBGs signal, and the strain gradient from microcracks.

Paper Details

Date Published: 16 April 2014
PDF: 12 pages
Proc. SPIE 9059, Industrial and Commercial Applications of Smart Structures Technologies 2014, 90590F (16 April 2014); doi: 10.1117/12.2045148
Show Author Affiliations
Scott M. Strutner, Univ. of California, Los Angeles (United States)
Frank Pena, California State Univ., Los Angeles (United States)
Anthony Piazza, NASA Dryden Flight Research Ctr. (United States)
Allen R. Parker, NASA Dryden Flight Research Ctr. (United States)
W. Lance Richards, NASA Dryden Flight Research Ctr. (United States)
Gregory P. Carman, Univ. of California, Los Angeles (United States)

Published in SPIE Proceedings Vol. 9059:
Industrial and Commercial Applications of Smart Structures Technologies 2014
Kevin M. Farinholt; Steven F. Griffin, Editor(s)

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