Numerical study of filling strategies in vacuum assisted resin transfer molding process

During the filling process of vacuum assisted resin transfer molding (VARTM), the infusion pressure gradient causes the resin flow and preform thickness variation. Even after the resin infusion discontinues, the resin keeps on flowing until the unnecessary resin is removed. In this study, a one-dimensional flow model coupled to the preform deformation is numerically analyzed to assess the influences of various processing scenarios on the infusion and post-infusion stages. The numerical model is implemented using a finite difference method. Results show that two strategies effectively reduce the filling process. One is to infuse less excess resin and the other is to turn the inlet into the additional vent. For a typical process using a one-sided vent, the theoretically optimum scenario is to infuse the exact required resin volume into the preform. From a practical standpoint, excess resin infusion is inevitable and a robust scenario is proposed by integrating the concept of fully filled preform and two strategies. Additional cases are performed using a vacuum assisted compression RTM (VACRTM) process for comparison purposes. Through the numerical work, a tool for optimization of the VARTM process is provided to reduce the filling process, resin waste and variability in the final composite part.