Modeling Race Tracking Effects in Liquid Composite Molding

Abstract

Fabrication of polymer composite components for automotive applications typically involve the injection of a reactive polymer resin into a preform placed in a closed mold. This process, generally referred to as liquid composite molding, offers the opportunity for part consolidation and fabrication of large, complex shaped parts in a single molding step. A problem often encountered in the molding of composite components is the channeling flow (or race tracking) of resin along the periphery of the preform. This race tracking flow occurs as a result of a small clearance between the preform periphery and the mold. The resistance to flow in the peripheral clearance is much smaller than that in the bulk preform; hence, resin preferentially flows through this region. This paper will present an integrated approach to modeling flow (both in the preform and along the periphery) in the mold cavity. The objective is to model race tracking as part of the overall flow problem. The solution essentially involves the interfacing of the two flow domains along the preform periphery. An integrated approach will not only lead to more accurate model predictions, but will also lead to improved computational efficiency. Example case studies will be presented to illustrate the importance of including race tracking in modeling liquid composite molding operations.