Exploratory development of VARIM process for manufacturing high temperature polymer matrix composites

This research focuses on an exploratory development of vacuum assisted resin infusion molding (VARIM) process for manufacturing high temperature polymer matrix composites for high speed civil transport. The present study involves development of a comprehensive process virtual model and a physical model to relate the process conditions to the evolved properties and defects in the molded composites. The virtual model consists of three modules: the resin infusion stage; the resin cure stage; and the cure dependant mechanical properties. The physical model investigates the feasibility of VARIM for fabricating high temperature polymer composites and the behavior of the process with the change in its parameters. Characterization of properties, defects, and internal structure of produced composites is the major thrust in this study.;A virtual model for simulating the polymer flow behavior during the infusion stage was developed and verified experimentally, with capabilities for prediction of flow pattern, under the vacuum bagging, and evolved defects. The developed model of thermal and cure analysis was used to get a complete temperature and cure histories of the molded composites. The mechanical properties as functions of degree of cure and time were determined for 5250-4-RTM resin and eight-harness carbon fiber mats.;Based on the developed virtual model and with the appropriate mold design, sound panels, with internal voids content less than 1%, were successfully molded. Thus, the VARIM process was found to be feasible for fabrication of high temperature polymer composites. The experimental investigation shows that post cure time and maximum cure temperature are the most significant parameters. Heating rate has a little effect on the process. As the maximum cure temperature decreases the material strength increases. Increasing post cure time from zero to five hours helps to increase the strength under high humidity and high temperature condition. The study shows that, within the range used for each parameter in the experimental design, a maximum cure temperature of 183°C, a post cure time of 5 hours at 227°C, and a heating rate of 1.67°C/min are the optimum process conditions for high-temperature and high-humidity applications. These curing conditions would maximize the mechanical properties of composites molded by VARIM.;The findings of this research will help in developing a science based technology for the VARIM process for understanding of the process behavior and the effects of various process parameters on the properties and integrity of the produced composites.