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

Abstract

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.

Numerical Study of Thin-Walled Polymer Composite Part Quality When Manufactured Using Vacuum Infusion with Various External Pressure Controls

“…This results in an unacceptable in- The functional relationship (20) between V f and h leads to the conclusion that such indicators of process quality as the thickness and homogeneity of the preform thickness will also be better for the process implemented in Mode 3 (see Figure 17). The functional relationship (20) between Vf and h leads to the conclusion that such indicators of process quality as the thickness and homogeneity of the preform thickness will also be better for the process implemented in Mode 3 (see Figure 17). The last two figures show that the final time interval between 240 and 360 min is characterized by a practically unchanged average value of Vf in controlled modes 2-4, which is explained by the slowing down and stopping of the resin flow.…”

“…However, an alternative way to avoid the disadvantages and difficulties of obtaining reliable results in the production of critical composite structures by such methods is to technically modify them, most often by introducing additional controllable parameters. Such technical solutions include the so-called pulsed vacuum infusion process, the use of a post-infusion dwell for about 2 h at high temperature [ 17 , 18 , 19 , 20 , 21 , 22 ], which allows reduced porosity and increased strength to be obtained. Nevertheless, the most effective and fairly widespread solution to the problem of improving the vacuum infusion process seems to be through the technology of controlled post-infusion external pressure, proposed and studied on samples in [ 23 , 24 ].…”