A new numerical procedure to predict dynamic void content in liquid composite molding

High fiber tow count fabrics have been developed by fiber and fabric suppliers to meet automotive cost and performance requirements when manufacturing structural automotive composite parts at high production rates by resin transfer molding (RTM). Impregnation of these large fiber clusters may lead to local incomplete saturation of fabrics. Mechanical softening, early failure, or part rejection because of high voids content may be expected. As RTM is getting closer to become available for industrial high production rates of structural composite parts, simulation tools including void content predictions are receiving more attention. The present work proposes a new numerical procedure to predict dynamic void content in liquid composite molding (LCM) processes. The concepts of air bubbles entrapment and critical pressure for void mobilization are introduced. Good agreement was found for a particular resin/tow surface contact with experimentally measured unsaturated volumes for 1D flow. The calculations highlight the idea that fast injections could lead to low global void content but very high local void content.