Experimental investigation of high fiber tow count fabric unsaturation during RTM

High fiber tow count fabrics have been developed by fibers and fabrics suppliers to meet automotive cost and performance requirements when manufacturing structural automotive composite parts at high production rates by RTM. Impregnation of these large fiber clusters may lead to local incomplete saturation of fabrics. Mechanical softening, early failure, or part rejection because of high voids content may be expected. A new experimental method has been proposed to measure the air volume entrapped within the wetted part of the fabric at any given time and to quantify air entrapment kinetics. An important observation is that the whole unsaturation grows linearly with time for 1D flow. The modified capillary number has been correlated to the amount of air entrapped during the injection process. However, results of this study show that it cannot account for void mobilization and elimination. A critical pressure for the onset of void mobilization has been identified for one fluid/preform combination. This experimental work carried out with proper calibration provided the evidence that for high modified capillary number, a decrease in void content is to be expected.