Contribution to temperature and strain measurement optimization using optical fiber Bragg gratting sensor : application to composite fabrication process by resin infusion ; 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

thèse en co-tutelle entre les Mines de Saint-Etienne, et les Mines d'Albi. ; 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 ...