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Proceedings Paper

Monitoring of non-homogeneous strains in wood glued joints with embedded FBG optical sensors in mode I delamination tests
Author(s): R. S. Maciel; O. Frazão; J. J. L. Morais; J. R. A. Fernandes
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Paper Abstract

In this work it is presented a study of the reflection spectra yielded by a Fiber Bragg Grating sensor embedded into an epoxy glue line between two wood arms, in a double cantilever beam (DCB) Mode I delamination test. The reflection spectra were obtained using a Spectral Analyzer Fibersensing Bragmeter FS2200SA in regular time intervals, as the stress applied to the laminates is continuously increased until fracture occurs. They initially show a typical Bragg grating reflection spectrum, which gradually changes into more complicated, multiple-peak spectra, resulting from a non-homogenous strain distribution along the board line. Based on these results, a model was derived for the variation of the grating effective index which fits the observed spectra when the irregular strain distribution is observed. This model consists of usual cosine description of Bragg grating effective index with linear phase variation, plus a logarithmic phase change along the fiber length, resulting in the increment of the grating wavelength with increasing distance from the load application point. Moreover, from this model the strain distribution along the grating is found, yielding the expected result.

Paper Details

Date Published: 18 November 2013
PDF: 5 pages
Proc. SPIE 8785, 8th Iberoamerican Optics Meeting and 11th Latin American Meeting on Optics, Lasers, and Applications, 8785FQ (18 November 2013); doi: 10.1117/12.2031893
Show Author Affiliations
R. S. Maciel, INESC TEC (Portugal)
O. Frazão, INESC TEC (Portugal)
J. J. L. Morais, Univ. de Trás-os-Montes e Alto Douro (Portugal)
J. R. A. Fernandes, INESC TEC (Portugal)
Univ. de Trás-os-Montes e Alto Douro (Portugal)

Published in SPIE Proceedings Vol. 8785:
8th Iberoamerican Optics Meeting and 11th Latin American Meeting on Optics, Lasers, and Applications
Manuel Filipe P. C. Martins Costa, Editor(s)

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