Resin microwave preheating in liquid composite molding process

Liquid Composite Molding (LCM) is one of the most widespread Out-Of-Autoclave (OOA) class of processes used to manufacture components in composite material. In this process a dry preform of fibers is impregnated by a flow of liquid resin, which is forced to move through the reinforcement by a pressure gradient. One of the most challenging aspects in LCM processes is to achieve a complete impregnation of the reinforcing fibers. Unsatisfactory impregnation can occur at different scales, in terms of dry spots (macro scale), entrapped air between the tows (meso scale), or inside the tow between the fibers (micro scale). In order to achieve an acceptable component, the preform must be saturated at each scale. Due to this reason, the necessity to enhance the flow in LCM processes arises. The aim of this work is to investigate the capability of microwave preheating to improve the resin flow in a Vacuum Assisted Resin Transfer Molding (VARTM) process. In particular, the resin is forced to pass through the resonant cavity of a microwave heater before the impregnation, in order to increase its temperature and reduce its viscosity. Feedback signals are collected by thermocouples, positioned into the pipes, and dielectric sensor, embedded in the die.