Monitoring high-pressure silicone oil flow using fibre Bragg gratings for fast manufacturing of composite materials

High-pressure resin transfer moulding is a novel process to manufacture composite materials, having the advantages of allowing fast moulding speed and strong part performance. One of the most significant difficulties of the process is that the flow of resin used inside a closed mould cannot be directly monitored. In this paper, a fibre Bragg grating (FBG) sensor is embedded into the glass fibre layers placed inside the mould with the purpose of monitoring the resin flow in the process. This is achieved by heating the mould and measuring how the cold resin flows through the mould using a series of FBG sensors. Results find out that the FBG peak wavelength sharply decreases when the resin reaches the position of the sensor, allowing the monitoring of the flow front through a closed mould. The method is validating comparing FBG measurements with camara recording to visualise the actual position of the fluid. Although FBG sensors respond to both temperature and strain changes, the sharp thermal impact can be easily detected, making unnecessary any temperature-strain discrimination.