Regulating Filling Pattern for Optimum Design of Resin Transfer Molding

During resin transfer molding (RTM), dry spot formation and air entrapment during the filling stage often lead to inferior parts and high scrap rate. These problems are usually caused by improper design of inlet conditions and vent locations that prevent the Last Point to Fill (LPF) location from coinciding with the preset vent location. This paper presents a methodology to design the RTM process with a desired filling pattern free of dry spots. Unlike the traditional filling simulation that predicts the filling pattern using prescribed inlet conditions and the specification of the preform permeability field, this methodology calculates the optimum inlet conditions based on the specification of the desired filling pattern and the prescription of preform permeability. The use of this algorithm greatly enhances the process design capability by reducing trial-and-error procedures that use traditional direct filling simulation as a primary process design tool. The numerical algorithm is described along with RTM design example showing that use of the proposed methodology results in the LPF location coinciding with the preset vent location.