ABSTRACT
The use of atmospheric pressure to hold closed molds together during injection was the early process of vacuum assisted resin injection (VARI). Adding vacuum has enabled resintransfer molding (RTM) to challenge compression molding and autoclaving systems capable of making the best high-performance composites. Vacuum is used in two ways. First, it mixes resin and hardener under a 91-Pa vacuum just prior to injection. Using an impeller, it agitates the mixture to drive air to the surface where the vacuum removes it. Degassing, which takes about 2 h per tank, also removes volatiles and low-molecular-weight by-products.
