Impregnation and saturation analysis of microwave‐preheated reactive resin in liquid composite molding

In liquid composite molding processes, resin preheating is a strategy to reduce the viscosity, which consequently improves resin flow and reduces impregnation time. However, the provision of heat to thermoset systems must be carefully calibrated since polymerization is activated by thermal energy, and premature resin curing would determine a sharp increase in viscosity and ineffective impregnation of the reinforcement. This work aims to study the resin flow in the realization of thermoset matrix composites through microwave-preheated liquid composite molding. Experimental and numerical analyses have been conducted to compare the microwave-preheated and the unheated resin infusion in closed molds. The impregnation and saturation were detected by dielectric sensing. The numerical simulation of the process evidences the effects related to the reactivity of the thermoset resin system. The experiments conducted highlight a reduction in filling time of 20% and in saturation time of 15% due to the beneficial effects of preheating in the analyzed cases. Highlights: Microwave preheating accelerates the unsaturated flow in resin infusion. A numerical model was implemented to replicate the reactive resin flow. Reinforcement permeability and resin reactivity have been characterized. The saturation rate of the reinforcement is not sensibly influenced by preheating. Preheating determines higher pressure gradients, improving the flow advancement.