Closed form solution of resin flow from multiple line gates in liquid composite molding

Abstract The resin flow from multiple line injection into a fibrous porous medium is investigated analytically and experimentally. The flow in a rectangular porous medium is created by placing two inlets: a channel along one of the domain edges, and a manifold placed in the center of the domain perpendicular to the first inlet on the top surface of the porous medium. It is demonstrated that two distinct sub‐regions of the porous medium exist: inner sub‐region which is filled by the liquid from the manifold, and outer sub‐region that is filled by fluid from the channel. In the experiments, the following geometric parameters are varied: channel cross‐sectional area, mold width, and thickness to investigate how the processing parameters influence which part of the overall domain is filled by fluid from a specific inlet. Neither fluid nor porous medium are varied throughout the study. For nonconstrained flow, an analytical model is formulated to predict the interface between the two sub‐regions which is called the inner sub‐region thickness. Both, implicit and explicit solutions are found, where the explicit solution is represented as inverse Lambert function. The solution relies on one physical constant which is a function of the pressure gradients and the directional permeabilities of the fibrous preform. Comparisons between experimental and analytical results reveal an excellent agreement for various sets of geometric parameters. This research should prove useful in understanding the flow in composites manufacturing when resin is injected simultaneously from multiple gates and channels. POLYM. COMPOS., 31:1434–1441, 2010. © 2009 Society of Plastics Engineers