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Développement d'un capteur à fibre optique à base de réseaux de Bragg superposés de courtes et de longues périodes : application à la mesure discriminée de température et de déformation

Abstract : [Optical Fibre Sensors present some interesting qualities when considering its size and weight relatively light, which lead to a low intrusivity of the sensor in a material (a composite structure). These sensors are insensitive to electromagnetic phenomenon, stable and long lasting with time, but sensitive to several solicitations such as temperature, strain and pressure hence a real need of discrimination. Among these sensors, we may discern the Bragg gratings: the Long Period Grating one (LPG) and the Fibre Bragg Grating (FBG) one. This thesis work reports the development of an optical fibre sensor based on two superimposed Bragg gratings: LPG and FBG for measuring and discriminating temperature and strain. Several studies are reported in literature without getting a real condition use. That's why we propose a parameter E, which stand for the discrimination efficiency leading to a possible comparison of the existing techniques and highlight the quite good potential of superimposed Bragg gratings. The settings of such a structure are given in this thesis report and consist in writing LPG first, then FBG over the entire length of the LPG, which also gives multiplexing possibilities. Strain and temperature calibration steps give sensitivities errors of 2% for temperature and 3% for strain, which lead to estimated errors on measured strain and temperature of 0.3°C and 3 microstrain respectively. In an application point of view, the sensor has been used for the instrumentation of a metallic structure subjected to a variation of temperature and strain applied simultaneously. The results exhibit a maximum error of 0.4°C and 3me for temperature and strain respectively, which is a good validation of the sensor for structural control and monitoring purpose. The second studied application is about instrumentation of glass/epoxy composite specimen for monitoring manufacturing processes: VARTM (Vacuum Assisted Resin Transfer Moulding) and LRI (Liquid Resin Infusion), for which temperature and strain have been monitored with the superimposed Bragg gratings based sensor. Dielectric analyses have also been performed during those processes in order to compare and validate our results]
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Submitted on : Tuesday, April 17, 2012 - 10:12:58 AM
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  • HAL Id : tel-00688229, version 1

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Sébastien Triollet. Développement d'un capteur à fibre optique à base de réseaux de Bragg superposés de courtes et de longues périodes : application à la mesure discriminée de température et de déformation. Autre. Université Jean Monnet - Saint-Etienne, 2010. Français. ⟨NNT : 2010STET4018⟩. ⟨tel-00688229⟩

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