Flow front measurements and model validation in the vacuum assisted resin transfer molding process

Through-thickness measurements were recorded to experimentally investigate the through thickness flow and to validate a closed form solution of the re sin flow during the vacuum assisted resin transfer molding process (VARTM). During the VARTM process, a highly permeable distribution medium is incorp orated into the preform as a surface layer and resin is infused into the mo ld, under vacuum. During infusion, the resin flows preferentially across th e surface and simultaneously through the thickness of the preform, giving r ise to a three dimensional-flow front. The time to fill the mold and the sh ape of the flow front, which plays a key role in dry spot formation, are cr itical for the optimal manufacture of large composite parts. An analytical model predicts the flow times and flow front shapes as a function of the pr operties of the preform, distribution media and resin. It was found that th e flow front profile reaches a parabolic steady state 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 we re carried out using embedded sensors to detect the flow of resin through t he thickness of the preform layer and the progression of flow along the len gth of the part. The time to fil]. the part, the length of flow front and i ts shapes 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.