Optoelectronic characterization of the curing process of thermoset-based composites

In this paper, the optoelectronic characterization of the polymerization process of thermoset-based composites is described. As is well known, in the last decade, these kinds of material in the light of their low weight/mechanical strength ratio have been widely used in many industrial areas such as automotive, aeronautic and aerospace. Because of the dependence of their properties on the manufacturing stage, real-time monitoring of the curing process has been indicated as the key point for improving the quality and reducing manufacturing process costs. In fact, in situ identification of the status of the processed material would allow the implementation of an on-line control of the manufacturing stage, leading to the transformation of the classical process in a real scientific operation. Based on this line of argument, a less-contact optical technique has been used to monitor the refractive index variation of an epoxy-based resin due to the polymerization process. Starting from preliminary experimental results, a fibre optic sensor has been designed and developed in order to perform iii situ cure monitoring by refractive index measurement. A theoretical model has been developed and validated by comparison with calorimetric characterization.