An Analytical Vacuum-Assisted Resin Transfer Molding (VARTM) Flow Model
Final rept. Jan 1997-Jul 1999
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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A closed form solution for the flow of resin in the vacuum-assisted resin transfer molding VARTM process is used extensively for affordable manufacturing of large composite structures. During VARTM processing, a highly permeable distribution medium is incorporated into the preform as a surface layer. During infusion, the resin flows preferentially across the surface, simultaneously through the preform, to a complex flow front. The analytical solution presented here provides insight into the scaling laws governing fill times and resin inlet placement as a function of the properties of the preform, distribution media, and resin. The formulation assumes that the flow is fully developed and is divided into two areas 1 a saturated region with no cross flow, and 2 a flow front region, which moves with a uniform velocity, where the resin is infiltrating into the preform from the distribution medium. The law of conservation of mass and Darcys Law for flow through porous media are applied in each region. The resulting equations are nondimensionalized and are solved to yield the flow front shape and the development of the saturated region. It is found that the flow front is parabolic in shape, and the length of the saturated region is proportional to the square root of the time elapsed. The obtained results are compared to data from fill-scale simulation and show good agreement. The solution allows greater insight into the physics process, enables parametric and optimization studies, and can reduce the computational cost of full-scale, three-dimensional 3-D simulations.
- Metallurgy and Metallography