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Non-isothermal monitoring of strain build-up in thermoset processing by a single chirped fiber Bragg grating

A partially embedded chirped fiber Bragg grating has been used to monitor the strain build up during non isothermal curing of a model thermoset resin. The particular feature of the spectra of a linearly chirped and strongly apodized fiber Bragg grating to encode position along the sensor has been used to simultaneously measure temperature and strain during the cure cycle of an epoxy based polymer. In particular, the embedded part of the grating allows the monitoring of temperature and processing strain while the rest of the sensor is sensible to temperature variation only. A new self temperature referenced sensor system has been successfully tested in an operative condition where usually thermomechanical loading are simultaneously active. The onset and progression of gelification as well as the temperature have been measured.