Use of sensors and actuators to address flow disturbances during the resin transfer molding process

Abstract In Resin Transfer Molding a fiber preform is placed in a mold, the mold is closed and a thermoset polymeric resin is injected through gates into the mold to saturate the preform completely. The resin flow rate is controlled by actuators, which are usually injection machines. When one places the preform into the mold, the gap between the preform and the mold walls can create race tracking channels and provide the resin flow paths that can severely influence the flow patterns and drastically change the flow history. As this gap is unavoidable and not reproducible, one could have different strengths of this disturbance from one part to the next, some of which will cause incomplete saturation of the fibers by the resin. Hence, an active control of the filling stage is necessary that can detect and characterize the race tracking and provide the control action to redirect the flow with the aim to saturate the preform without resin starved regions (macro voids or dry spots). A methodology is proposed that intelligently places sensors in the mold to detect the resin arrival times at these locations. This information is used to determine and quantify the strength of the disturbance and used as an input parameter for the actuators to redirect the flow. This paper demonstrates this methodology on a simple mold configuration, and outlines how this technique can be generalized to any mold geometry or disturbance set in an automated RTM environment. Numerical simulations are used to establish the control methodologies, and all of the efforts are confirmed in a laboratory setting. The proposed methodology should prove useful in increasing the yield of Resin Transfer Molded parts.