Investigation of the role of transverse flow in co-injection resin transfer molding

A co-injection resin transfer molding (CIRTM) process has been developed at the University of Delaware's Center for Composite Materials in collaboration with the U.S. Army Research Laboratory. It enables two or more resins to be simultaneously injected into a mold filled with a stationary fiber preform. This process allows for the manufacturing of co-cured multi-layer, multi-resin structures in a single processing step. A separation layer is used to provide resin compatibility during cure and to control resin mixing. Scaling issues relating the role of transverse permeability in resin mixing are investigated. This study presents two different approaches taken to understand the causes of transverse flow and to quantify the amount of transverse now that occurs during processing. The first approach, a one-dimensional model, explains the important parameters that govern resin flow in CIRTM. The second approach is based on an existing finite element code that is modified to allow for the injection of multiple resins. The total amount of transverse flow was quantified using the finite element code. This research shows that the CIRTM process requires a totally impermeable separation layer if CIRTM is used to manufacture large parts and/or if the resins injected have significantly different viscosities.