Effects of Processing Conditions on Vacuum Assisted Resin Transfer Molding Process (VARTM)

The continued growth of vacuum-based processes has warranted the development of both models and experimental studies designed to capture the unique aspects associated with this manufacturing technique. To that end, this report summarizes an initial set of experiments that characterize both the process and the resulting mechanical properties of components fabricated under a variety of process conditions. Specifically resin flow studies are presented in part to demonstrate the relative influence of key parameters on the flow front developed during impregnation. The effect of the distribution medium, which is used in a commercial version of VARTM known as Seemans Composite Resin Infusion Molding Process SCRIMP, is explicitly characterized. In addition, the variation of part thickness is also examined, and potential mechanisms responsible for these variations are presented. A battery of mechanical tests designed to correlate the effect of various processing conditions are also presented. A major finding is that thickness variation can be significant and, to some degree, random also, precompaction of the preform significantly influences the amount of consolidation pressure needed during impregnation. Dimensional variations due to gradients in the pressure distribution of the vacuum affect permeability and hence resin flow, as well as dimensional tolerances in manufactured parts.