Flow control using localized induction heating in a VARTM process

Voids formed during the mold filling stage of the vacuum assisted resin transfer molding (VARTM) process become defects in the fabricated parts. Active flow control is one way to eliminate these defects by guiding the flow along a desired path during the mold filling stage of the process. Building upon previous work of the authors [Johnson R, Pitchumani R. In: Proceedings of the thirty-fourth international SAMPE technical conference, MD, USA, vol. 34(1); 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; Johnson R., Pitchumani R. In: Proceedings of the fourteenth international conference on composite materials, CA, USA; 2003, Paper# 0861; Johnson R, Pitchumani R. Simulation of active flow control based on localized preform heating in a VARTM process. Compos Part A-Appl Sci Manuf, in press doi:10.1016/j.compositesa.2005.09.007], this paper presents implementation of an active flow control using induction heating as a means of locally reducing viscosity to counteract the effects of nonhomogeneity in the permeability of preform layups in a prototype VARTM process. Feedback of flow front locations during the filling stage of the 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. A flow front following control strategy is implemented in a lab-scale experimental setup and tested on several preform layups exhibiting spatial permeability variation, as well as in the case of preforms with mold inserts. Results of these studies demonstrate that active flow control is capable of reducing the fill time, improving the flow front uniformity throughout the duration of the mold fills, and eliminating dry spot formation.