Simulation of active flow control based on localized preform heating in a VARTM process

Defects in parts produced by the vacuum assisted resin transfer molding (VARTM) process are often attributable to the formation of voids during the mold filling stage of the process. These defects can be eliminated through the use of active control schemes to steer the flow to follow a desired path. This paper builds upon previous work of the authors [Johnson R, Pitchumani R. Induction heating assisted permeation enhancement for the VARTM process. In: Proceedings of the 34th international SAMPE technical conference. Maryland; 2002. p. 250–61; Johnson R, Pitchumani R. Enhancement of flow in VARTM using localized induction heating. Compos Sci Technol 2003;63(15):2202–15] and explores the innovative idea of using induction heating as a means of locally reducing viscosity to counteract the effects of spatial permeability variations in preform layups. Feedback of flow front locations during the filling stage of the VARTM process is used together with a numerical process model to arrive at decisions on the trajectories of the induction coil, and the coil voltage, so as to maintain a uniform flow progression without exceeding a prescribed maximum temperature limit. In the present study, various control strategies are explored in a simulation environment to arrive at an optimal scheme for practical implementation. Results of studies demonstrate that the control scheme is capable of improving the flow uniformity, as measured by the root mean squared (RMS) error relative to an ideal uniform fill by as much as 88% in comparison to an uncontrolled mold fill, while simultaneously maintaining acceptable material temperatures throughout the filling process.