Process Improvements for the Resin Transfer Molding of Composite Intake Valves for Internal Combustion Engines

摘要

In previous work, composite intake valves for use in internal combustion (IC) engines were manufactured by resin transfer molding (RTM) and demonstrated in a fully functional IC engine on a dynamometer. These valves consisted of a high temperature polyimide matrix, LaRC PETI-RFI, reinforced with a carbon fiber preform. While this previous work successfully demonstrated the potential for composite intake valves, several issues were noted including excessive surface porosity on the stem and head of the valves. It was hypothesized that the porosity developed during the cure stage of processing was a result of inadequate process pressure due to a lack of sealing in the resin transfer die. In the current work, improvements to the sealing of the die have been made in an attempt to evaluate the effectiveness of pressure generated from differential thermal expansion of the polyimide matrix and the die during the cure stage. Additionally, the development of preforms resulting in higher fiber volume fractions, a transition to the lower viscosity polyimide, LaRC PETI-RTM, and the utilization of vacuum-assist during resin transfer molding were investigated to assess the effects on the as-molded surface quality. The results of this processing study suggest that, with continued process development in the areas outlined, high quality, porosity-free composite intake valves can be manufactured by resin transfer molding.