Experimental Investigation of the Effect of Fiber-mat Architecture on the Unsaturated Flow in Liquid Composite Molding

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Abstract
In liquid composite molding technologies such as RTM, this study of the inlet-pressure history for the constant flow-rate 1-D flow experiment reveals that the measured pressure profile, which droop downwards as in earlier studies on the unsaturated flow, is at a variance with the linear pressure profile predicted by the physics used for state-of-the-art LCM mold filling simulations. The droop along with the error in the inlet-pressure predictions increase with an increase in the fibermat compression. The effect of fiber-mat architecture on the droop in the inletpressure profiles is studied and significant droops are observed for various stitched mats as compared to the woven mats. This study repudiates the long-held view that mere presence of cylindrical or elliptical tows in the woven or stitched fiber-mats automatically leads to the unsaturated flow characteristic of dual-scale porous media; rather the presence of continuous uninterrupted macrochannels along the flow direction for preferential channel-flow is found to be necessary for the appearance of a drooping inlet-pressure history characteristic of the unsaturated flow.

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