Test equipmentLiquid Resin Infusion process monitoring with superimposed Fibre Bragg Grating sensor

This paper reports on the instrumentation and monitoring of a fibreglass/epoxy composite manufacturing process using an optical fibre sensor based on a Bragg grating. The sensor is made of superimposed Long Period Grating (LPG) and Fibre Bragg Grating (FBG), both written on the same fibre zone. This sensor gives very accurate results and good spatial resolution due to its ability to discriminate intrinsically between thermal and kinematic effects. The sensor was initially tested during the curing of an epoxy resin alone in order to assess temperature and strain measurements. It is shown that these two factors can be well discriminated and quantified. The paper then presents results for monitoring Liquid Resin Infusion (LRI), with the FBG/LPG sensor embedded in a composite part. Dielectric analysis was also performed. Results and analyses of the thermal cycle of curing and induced residual strains are discussed.