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Contribution à l'optimisation des mesures de température et de déformations par capteur à fibre optique à réseau de Bragg : application au procédé de fabrication des composites par infusion de résine

Abstract : In the first part, we point out that composite material processes can be monitored thanks to optical fiber Bragg grating sensors (FBG) embedded into the material for strain and temperature measurement. In the second part, the principle and physics of FBG sensors and their sensitivity are detailed. FBG sensors measurements are analyzed in order to optimize measurement uncertainties. These uncertainties can be induced by several factors : the system used for signal acquisition, the method used to analyze the FBG spectrum, the FBG calibration step. In order to improve the FBG spectrum analysis, we have estimated the uncertainties induced by sampling, acquisition conditions, and evaluated different mathematical models and fitting methods. In order to achieve an accurate calibration of the sensor, an experimental bench permitting to apply a mechanical tension to the optical fiber under a thermally controlled environment has been developed. Some sensor characteristics like non-linearity, cross sensitivity and thermal drift have been also studied. Optical fiber intrusivity is studied. The results based on the observation of the optical fiber introduced in the composite host material and especially the carbon fiber organizations around FBG sensor are presented. FBG sensors are sensitive to temperature and strain simultaneously. A bibliographical review of different methods for strain/temperature discrimination is proposed. Two solutions have been selected and developed in our work : the first one is based on the use of a thermocouple associated to the FBG, and the second one is based on two Bragg gratings superposed at different wavelength on the same fiber. These solutions have been firstly evaluated for strain and temperature monitoring during the epoxy resin conversion. Secondly, FBG sensors have been used within the composite fabrication by resin infusion process known as LRI (Liquid Resin Infusion) in order to monitor the temperature and strain cycle during the cure. The last part of the document deals with the study of strain and temperature gradients (non homogenous parameters along the fiber) based on the analysis of the whole FBG spectrum. A gradient identification method inspired by the T-Matrix direct method, which computes simulated spectrums, is proposed. The identification method has been validated firstly on numerical cases, and secondly by experimental work thanks to a setup specially designed to apply thermal or mechanical gradients along the sensor.
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https://tel.archives-ouvertes.fr/tel-00440938
Contributor : Mustafa Demirel <>
Submitted on : Monday, December 14, 2009 - 9:36:19 AM
Last modification on : Thursday, February 27, 2020 - 1:18:14 AM
Document(s) archivé(s) le : Thursday, June 17, 2010 - 9:39:37 PM

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  • HAL Id : tel-00440938, version 1

Citation

Mustafa Demirel. Contribution à l'optimisation des mesures de température et de déformations par capteur à fibre optique à réseau de Bragg : application au procédé de fabrication des composites par infusion de résine. Sciences de l'ingénieur [physics]. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2009. Français. ⟨tel-00440938⟩

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