ANALYSIS OF THE RESIN TRANSFER MOLDING PROCESS USING IN-MOLD DIELECTRIC SENSORS

Interest in the potential use of resin matrix composites for structura l automotive components has grown dramatically in the last five years. This has been evidenced by the formation of an Automotive Composites Consortium with the General Motors and Chrysler Corporations and the F ord Motor Company to investigate these materials. Efforts are under wa y within these member companies to study material properties, processi ng procedures, and energy management phenomena in order to allow the d esign of viable structural vehicle components, e.g. crossmembers, bump er beams, and front-end rails, utilizing resin transfer molding (RTM). While progress is being made in all these areas of investigation, it is extremely important that processing feasibility be adequately under stood and demonstrated. It is particularly necessary to understand and control the curing process in the mold in order to project acceptable cycle times. In this investigation, a temperature, pressure, and cure (dielectric) sensor was mounted in the surface of an RTM mold. The cu re behavior, mainly time to viscosity minimum and vitrification (deter mined from the dielectric data), was monitored as a function of variou s process parameters. These included mold temperature, resin pressure, resin chemistry, part thickness, and reinforcing fiber fraction. Resu lts of cure sensitivity to the various controlled parameters and exper iments with controlled press opening will be presented. Dielectric sen sor output was shown to be an excellent indicator for controlling pres s opening based on the vitrification event.