Experimental and theoretical studies of fabric compaction behavior in resin transfer molding1

Experimental and theoretical studies have been conducted on the compaction behavior of fabric preforms in the resin transfer molding process. Compaction experiments were carried out for three types of preforms, i.e. continuous strand mats, plain woven fabrics, and unidirectional knitted materials. The major factors contributing to the preform compaction behavior were identified. Then, in-situ contact pressure between adjacent fabric layers during compaction was measured using a TekScan system. The results of the pressure measurement motivated the improvement in the existing compaction model. Thus, the theoretical part of this paper focuses on modeling the compaction behavior of woven-fabric preforms with uniform, linear, and sinusoidal inter-layer contact pressure distributions. Analytical expressions for the relations among the fiber volume fraction, the applied compressive force, and the preform thickness reduction, have been established. Finally, the improved model is applied to predict the geometry of the resin channels of the preform under compaction. This knowledge can be readily used for evaluating the resin permeability as a function of applied pressure in the resin transfer molding process.