Resin flow monitoring in resin film infusion process

The resin film infusion is a promising and low cost technique for the manufacturing of high performance polymer-based composite materials. The processing cycle is usually performed in the autoclave where, under temperature and pressure application, a bagged dry fiber mat is infiltrated by a thermoset polymer resin which is pre-shaped in film form under the fibers. After complete infusion, the consolidation step behaves as in the conventional autoclave process. The infusion process is strongly affected by the permeability of the fiber mat that determines processing issues, such as the cycle time and the complete fiber impregnation and, as a consequence, the performance of the final part. Therefore, the permeability measurement represents one of the most crucial requirements for the design and the optimization of the composite manufacturing by RFI. In this study, a non-conventional technique, based on a fiber optic sensor, has been used to guess the permeability of braided carbon fiber fabrics infiltrated with an epoxy resin by reproducing experimental conditions similar to the RFI industrial manufacturing. The fiber optic sensor, placed through the reinforcement, is able to detect the resin advancement during the infiltration by recording the light intensity drop which takes place as the resin reaches the optical fiber location. This technique represents a valid alternative to the common permeability measurement methods based on flow visualization and in addition, it can be easily used for the real time monitoring of the resin flow advancement during the real processing.