A co-injection resin transfer molding (CIRTM) process has been developed at
the University of Delaware's Center for Composite Materials in collaborati
on 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 pref
orm. This process allows for the manufacturing of co-cured multi-layer, mul
ti-resin structures in a single processing step. A separation layer is used
to provide resin compatibility during cure and to control resin mixing. Sc
aling issues relating the role of transverse permeability in resin mixing a
re investigated. This study presents two different approaches taken to unde
rstand the causes of transverse flow and to quantify the amount of transver
se 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 mod
ified to allow for the injection of multiple resins. The total amount of tr
ansverse flow was quantified using the finite element code. This research s
hows 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.