Multiscale Flow Modeling and Simulation to Predict Void Formation and Transport in Composite Manufacturing

During composite manufacturing, polymeric resin is combined with fibrous reinforcement to form a composite structure. In almost all composite-manufacturing processes, from liquid molding to prepreg consolidation, resin is introduced in the liquid state or has to be converted to the liquid state with the application of heat, to occupy all the empty space between the fibers. Voids usually flow around fiber bundles, or tows, in a preform as opposed to flowing through them. It is possible for a void to become trapped between tows by the pressure gradient of the flow. In this case, the void would need to travel through the tows in order to escape. This paper models the void flow behavior inside of tows as a function of key flow parameters. The micro-scale void velocity is compared to the macro-scale resin flow velocity to gage if the void will be trapped or if it can be flushed out from the tow.