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The effects of impurities on the generation of voids in composites fabricated by vacuum-assisted resin transfer molding was investigated to help reduce mechanical weakening in large structures. Impurities were intentionally inserted into laminates, which were then observed optically. Internal voids were generated in specimens with impurities of 2 – 3mm thickness. The voids grew as the impurities' thicknesses increased to 4 – 5 mm. The voids' diameters were proportional to the thickness of the impurity. Void generation was shown to depend on the thickness of impurities. Environmental control during vacuum-assisted resin transfer molding was shown to be important for ensuring the quality of the resulting composites.

This study investigated a flow rate control system for the vacuum-assisted resin transfer molding (VARTM) process. Using Darcy’s equation, the permeability of multiaxial glass fiber composites is predicted and experimentally confirmed. The resin velocity vector is inversely proportional to the fiber mat length and resin viscosity, but proportional to the fiber mat permeability. In this study, the permeability of the preform and viscosity of the epoxy resin were measured using multiaxial glass fiber by VARTM. The permeability and time for impregnation differed according to the fiber direction in the VARTM process. The results indicated the need for further study of reinforcement fiber permeability in VARTM processing design.