A model of two-phase resin and void flow during composites processing

The reduction of porosity during composites manufacturing remains a critical design goal for successful processing. High porosity composite parts exhibit reduced mechanical properties and increased design risk. A primary source of porosity is the formation and transport of trapped air bubbles during polymer resin flow through fibrous porous media reinforcement. A model experiment has been developed in which a flow cell comprised of two transparent parallel plates is injected with a simulated resin and air bubbles to investigate two-phase flow. The flow cell is designed to simulate flow behavior exhibited during Resin Transfer Molding (RTM) or Out-of-Autoclave (OOA) prepreg composites processing. A flow visualization setup captures the two-phase resin flow and void migration through the flow cell. A computational model is formulated to describe the two phase flow and validated with experimental results. The model material and process parameters can be optimized to maximize the relative void velocity with respect to the resin, thus achieving effective void migration and overall porosity reduction during processing. A parametric scaling analysis is conducted to identify and quantify the sensitivity of material and process parameters on two phase resin and void transport in composites processing.