Effects of post-infusion dwell on vacuum infusion of thermoset composites toughened by thermoplastic interlaminar veils

The effects of post-infusion dwell on vacuum infusion of thermoset composites toughened by non-woven thermoplastic interlaminar veils were investigated. Permeability measurements and simulation of the resin infusion process demonstrated that the toughening interlayers can effectively act as interlaminar flow distribution media. Local variations in permeability induced non-uniform flow fronts, resulting in high porosity. However, introduction of a low-temperature post-infusion dwell allowed more time for the resin to equilibrate pressure and redistribute during the post-filling stage, achieving full saturation of dry regions. The process parameters of the post-infusion dwell were determined using cure kinetics and viscosity models, while in situ process adjustments were implemented using dielectric cure monitoring system in conjunction with resin cure maps. Laminates fabricated with the modified cycle exhibited reduced porosity and greater peak load during impact testing. This work highlights potential advantages of the post-infusion dwell, which can similarly be applied to other vacuum infusion processes requiring a protracted post-filling stage.