Closed-loop flow control in resin transfer molding using real-time numerical process simulations

Real-time feedback control of resin flow through a fibrous preform during the mold-filling step of resin transfer molding offers an effective means of eliminating fill-related defects in the composite products. Process simulation models have played an indirect role in the control, either through off-line determination of the control parameters to be used during the process, or in the training of artificial neural networks that act as proxy simulators online with the process. This paper explores, for the first time, the use of on-the-fly finite-difference-based numerical solution of the partial differential equations governing the mold filling process, in a closed-loop flow control. The numerical simulations are used to forecast system response in real-time, in order to determine the best combination of flow rates at the injection ports so as to steer the flow through a target schedule during the process. The performance of the controller implemented on a lab-scale resin transfer molding process is demonstrated on several preform configurations and desired fill patterns. The study paves the way for better utilization of the advances in process modeling and computational infrastructure toward an effective bridging of the science and practice of composites processing.