Effects of the addition of a cover mold on resin flow and the quality of the finished product in vacuum‐assisted resin transfer molding

Abstract

For vacuum-assisted resin transfer molding (VARTM), we propose adding a cover mold, inserted between the distribution medium and the peel ply, to achieve a higher fiber volume fraction in the final product. As the conventional VARTM process does not use a cover mold, improved processes using different rigid covers were explored. A three-dimensional digital image correlation system was developed to monitor the thickness evolution of the vacuum package during the infusion stage. This system was validated as a fullfield displacement test. The results demonstrate that there are three advantages to using a cover mold. First, in the filling stage, a rigid cover mold can prevent shrinkage of the part at the resin flow front, and even cause slight expansion of the unsaturated part. This improves the resin flow and shortens the time required for complete infusion. Second, a cover mold can limit the amount of excess resin needed to infuse the saturated part. Third, in the postfilling stage, the cover mold can be used to accelerate extrusion of the excess resin in the package. The overall effect is to increase the fiber volume fraction in the final product.

Monitoring and modeling of part thickness evolution in vacuum infusion process

“…29 Photogrammetry methods have proven to be useful for full field measurement of part thickness in VI. These non-contact methods are based on either the use of multiple cameras as in the case of speckle stereophotogrammetry 13,[30][31][32][33][34][35][36] or the use of a projector and a camera in Structured Light Scanning (SLS). 37 Despite allowing the measurement of full field thickness distribution, the photogrammetry approaches require more advanced algorithms to derive the thickness distribution from the recorded images.…”

Dynamic pressure control in VARTM: Rapid fabrication of laminates with high fiber volume fraction and improved dimensional uniformity

“…Actively controlling the pressure at the inlet/exit after the complete mold filling has been proposed as a possible method to reduce the thickness variation along the laminates . Various other approaches such as placing a caul plate on the preform or applying a constant external pressure were utilized to reduce the thickness variation . Despite modest improvements in dimensional uniformity, most of these methods did not considerably improve the overall compaction of the preform.…”

An Enhanced Vacuum-Assisted Resin Transfer Molding Process and Its Pressure Effect on Resin Infusion Behavior and Composite Material Performance

“…Various factors such as mold dimensions and structures, fiber preform design, type, layering, stacking sequence, pressure gradient distribution, and more all impact the flow of resin within the VARTM process. Therefore, improvements in the VARTM process primarily focus on these aspects and can be summarized into three main methods: (i) heating the resin to reduce its viscosity [1][2][3][4][5][6]; (ii) adjusting the pressure distribution on the mold surface [7][8][9][10][11]; and (iii) making the fiber prefabricated parts loose to increase the permeability [12][13][14][15][16][17][18][19].…”

“…Hence, some scholars have proposed the dual vacuum bag method, created two separate sealed chambers, and controlled the vacuum pressure in these inner and outer chambers to allow for the fiber preforms to relax and improve their permeability [12,13]. Others have used external rigid vacuum chambers above the mold to extract a certain degree of vacuum, thereby increasing the permeability of the fiber preforms to improve resin flow patterns [2,[14][15][16][17][18][19].…”