All fibre optoelectronic sensor with Bragg gratings for in situ cure monitoring

Real-time, in situ. monitoring for quality control of the polymer cure process is of high interest, since thermoset polymer-matrix composite are widely used in large industrial areas: aeronautical, aerospace, automotive and civil due to their low cost/low weight features. However, their final properties are strongly dependent on the processing parameters, such as temperature and pressure sequence. The key-point for advanced composite materials is the possibility to have distributed and simultaneous monitoring of chemoreological and physical proprieties during the cure process. To this aim, we have developed and rested an optoelectronic fibre optic sensor (FOS) based on the Fresnel principle able to monitor the variations of the refractive index due to the cure process of an epoxy based resin. Experimental results have been obtained on sensor capability to monitor the cure kinetics by assuming the refractive index as reaction co-ordinate. The integration with in-fibre Bragg grating (BG) in order to measure the local temperature has been discussed and tested.