Active control of reactive resin flow in a vacuum assisted resin transfer molding (VARTM) process

Flow of a catalyzed resin into a fibrous preform is an important step governing the quality of composite parts fabricated using liquid molding techniques. This article presents numerical and experimental investigations on novel means of active flow control to steer the resin flow through the preform so as to eliminate void entrapment and dry spots. The active control is based on locally heating resin to reduce viscosity and, thereby, enhance preform permeation at locations of flow lag in the preform throughout the filling process. A consequence of heating the reacting resin is an accelerated cure reaction that irreversibly increases resin viscosity with cure. A balance between the competing sources of viscosity change form the basis for the model-based control of localized heating. Focusing on a vacuum assisted resin transfer molding (VARTM) process, numerical modeling is coupled to an active control strategy in a simulation environment, and parametric studies are presented over a range of preform lay-ups and constraint on the maximum cure levels at the completion of the filling stage. In addition, the active control system is experimentally implemented and is shown to be successful in fabricating composite panels, without void entrapment or premature resin gelation, while reducing fill time and resin wastage.