Experimental Validation of a Closed-Form Fluid Flow Model for Vacuum-Assisted Resin-Transfer Molding

Abstract

Abstract : Through-thickness measurements were recorded to experimentally investigate the through-thickness flow and to validate a closed-form solution of the resin flow during the vacuum-assisted resin-transfer molding (VARTM) process. During the VARTM process, a highly permeable distribution medium is incorporated into the preform as a surface layer, and resin is infused into the mold, under vacuum. During infusion, the resin flows preferentially across the surface and simultaneously through the thickness of the preform, giving rise to a three-dimensional flow front. The time to fill the mold and the shape of the flow front are critical for the optimal manufacture of large composite parts. An analytical model predicts the flow times and flow-front shapes as a function of the properties of the preform, distribution media, and resin. It was found that the flow-front profile reaches a steady state shape that is parabolic in shape and the length of the region saturated by resin is proportional to the square root of the time elapsed. Experimental measurements of the flow front in the process were carried out using embedded sensors to detect the flow of resin through the thickness of the preform layer and the progression of flow along the length of the part. The time to fill the part, the length of flow front, and its shape show good agreement between experiments and the analytical model. The experimental study demonstrates the need for control and optimization of resin injection during the manufacture of large parts by VARTM.