Integrated fiber optic sensing system for in-situ characterization of the curing process of thermoset-based composites

Abstract

In the last decade, in light of their superior mechanical properties advanced polymer matrix composites have been indicated as the most suitable candidates as Smart Materials and Structures. However, their final properties are strongly dependent on the processing stage and key points to improve the quality and the reliability of these materials that have been identified in the cure monitoring and the optimization of the manufacturing process. Based on this line of argument, an integrated fiber optic sensing system for simultaneous refractive index and temperature measurements has been designed and developed in order to monitor the curing process of thermoset based composites. A fiber optic refractometer has been designed by using the free end of the sensing optical fiber. A theoretical model has been developed for converting refractive index changes in detailed information on the extent of the curing. Its validation has been proved by comparison with calorimetric characterization. In addition, integrated fiber Bragg gratings has been used for local temperature measurements. The interrogation of the sensing Bragg grating has been implemented by using a different fiber Bragg grating able to convert the resonance wavelength shift in intensity changes. Preliminary results are presented.