Development of adaptive injection flow rate and pressure control algorithms for resin transfer molding

To prevent dry spot formation during fabrication of composite parts by Resin Transfer Molding (RTM), a control interface and four different adaptive control algorithms have been developed and tested with numerical simulations. The interface is capable of controlling the flow pattern of resin as it fills a mold containing a preform of fiber reinforcement, provided that the mold is equipped with multiple inlet gates, a single vent and a spinal sensor system that continuously feeds the interface with the resin flow front locations along the spine lines connecting the inlet gates to the vent. Four different adaptive control algorithms targeting on injection flow rate control, injection pressure control, linearly-corrected pressure control, and the combined flow rate and linearly-corrected pressure control have been proposed and incorporated with the control interface. To provide desirable controllability of the filling process and effective utilization of the resin dispensing equipment, the final formulations were optimized by means of numerical simulations of a rectangular RTM part containing different permeability distributions. The results were compared to investigate the strengths and weaknesses of the spinal adaptive control algorithms in terms of dry spot size, filling speed, and the minimum responding speed of injection pump. Finally, a complex geometry case study was conducted to validate and highlight the spinal adaptive control algorithms’ capability in handling flow disturbance for a complex RTM mold filling process which involves irregular mold geometry, multiple inserts, significant permeability and racetracking variations, and non-straight spinal sensors.