Statistical characterization and robust design of RTM processes

In RTM process, major quality problem comes from unbalanced resin flow in mold filling process. Fiber preform permeability is the key parameter influencing the resin flow behavior. On the other hand, due to the variations existed in the raw materials and processing, the preform permeability varies across the regions within a part and from part to part. This variability results in reduced reproducibility of the composite components made by RTM. It is imperative to understand the statistical behavior of the permeability variations of preform in typical RTM processes. In this research, a comprehensive study was conducted to investigate the statistical property of the typical flow disturbance due to race-tracking in RTM processes. It was found that the ratio of the permeability values caused by race-tracking over average value for a rectangular mold could be represented as Weibull variables. With the statistical analysis results, a robust RTM process design method was introduced and illustrated. This new process design approach can help design RTM processes to be insensitive to preform permeability variations coming from materials and processing. Therefore, high quality composite components can be made consistently.