Glass optical fibre sensors for detection of through thickness moisture diffusion in glass reinforced composites under hostile environments |
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Authors: | B Milsom M Olivero D Milanese S Giannis R H Martin A Terenzi |
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Affiliation: | 1. Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italyb.milsom@qmul.ac.uk;3. Department of Electronics and ecommunications, Politecnico Di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy;4. Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy;5. Element Materials Technology Ltd, Wilbury Way, SG4 0TW Hitchin, UK;6. M.D.P Materials Design &7. Processing S.r.l., Loc. Pentima Bassa, 21, 05100 Terni, Italy;8. Civil and Environmental Engineering Department, University of Perugia, Strada di Pentima, 4, 05100 Terni, Italy |
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Abstract: | A combination of evanescent wave optical sensors (EWOSs) and fibre Bragg gratings (FBGs) were embedded in an epoxy vinyl ester and an epoxy vinyl ester based glass reinforced polymer (GRP) composite to measure fluid ingress that would result in degradation under hostile conditions. Samples were subjected to accelerated aging in the form of single sided exposure to simulated sea water at 120°C in a pressurised stainless steel vessel. Low cost EWOSs were prepared from a standard multimode glass optical fibre and compared to commercially available FBGs. Both sensors were able to detect the early stage of moisture diffusion into the GRP matrix. The evanescent sensors showed a reduction in the transmitted signal intensity between 1500 and 1650?nm with an increasing exposure time due to a change in the optical properties of the polymer, whereas a peak shift was observed for the FBGs due to the swelling of the resin with the absorption of water. Additionally, the glass optical fibre sensors were embedded in a configuration that allowed the extent of diffusion through the thickness of the GRPs to be monitored, with the fibres in the closest position to the exposure face showing a greater signal change than those positioned further away. |
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Keywords: | Glass fibre optic sensors Environmental degradation Evanescent sensors |
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