Use of Flow Simulation for Design, Optimization and Control of Liquid Composite Molding Processes

摘要

Science based flow simulations are being routinely used before a new prototype is designed and the prototype manufacturing process is established. As the complexity of composite structure increases, the yield from a production process decreases. This outcome stems from the variability associated with the fiber preform resistance to resin flow around the walls of the molds or inserts that are placed in the mold as the resin tries to impregnate the empty spaces between the fiber preform in the mold. This resistance is not repeatable as it depends on how the preform is cut and placed inside a mold. This paper shows how simulations can be extended to improve the yield by introducing optimization and control strategies to successfully fill a mold without voids. We introduce a passive control strategy in which the vent locations for the resin to arrive last are selected by conducting simulations of all possible permutations of anticipated variations. However as one can only choose limited number of vents, the yield improvement will be modest. To ensure success in most of the cases, two active control strategies, scenario based control and dependence map based control are introduced. Both strategies rely on flow arrival sensor feedback and use of auxiliary actuators to redirect the resin in areas that are unfilled. Scenario based control is based on anticipating the disturbance sites where as dependence map based control relies on correcting the flow based on a target flow pattern. Simulations are used off-line to develop these strategies for the specific mold geometry and the results are transferred to a workstation that can implement them during the mold filling process in a laboratory experimental environment. Examples that demonstrate improvement in the filling behavior despite the disturbances are presented with experimental validation.