EFFECTS OF SIZINGS ON MICROSCOPIC FLOW IN RESIN TRANSFER MOLDING

Sizings significantly affect the processing and final performance char acteristics of resin transfer molded (RTM) parts. Manufacturers often use sizings to enhance compatability between the resin and reinforceme nt and to assist processing. In particular, such coatings can affect t he microscopic flow characteristics of resins during the infusion stag es of the RTM process. To understand the mechanisms by which sizings a ffect preform wet-out and the extent of such effects, the influence of fiber sizings and fiber loadings on the flow of a vinyl-ester resin s ystem, through axially aligned carbon fibers, have been measured. The results and analysis of the experiments reported herein form the basis for a phenomenological model that describes the effect of sizings on micro-flow in RTM. Furthermore, the work provides insight into the rel ationships among micro-flow, macro-flow, and preform infiltration. It is seen that sizings dramatically influence micro-impregnation and, fo r the flow configuration studied, radial micro-flow into fiber bundles was the rate limiting process for complete fiber bundle unfusion.