On the design of test molds based on unidirectional saturated flows to measure transverse permeability in liquid composite molding

Impregnating fibrous preforms through thickness has become a main feature of some liquid composite molding process variants. Thus, the evaluation of transverse permeability is critical to optimize the fabrication and reduce manufacturing defects. Some problems connected with the design of testing devices need to be addressed to perform a reliable characterization. In this study, the efficiency of a typical one-dimensional testing device to measure transverse permeability is evaluated numerically and experimentally. The paper introduces a novel methodology to identify the optimal mold configuration and evaluate the flow pattern inside the mold cavity. A dimensionless number called the "fill coefficient" is also proposed to evaluate quantitatively the effect of the mold structure on the transverse flow pattern. The measured transverse permeability is shown to increase with lower fill coefficients for saturated and unsaturated flows. The intrinsic transverse permeability is obtained when the fill coefficient is equal to one. The proposed methodology is verified by experiments performed in an existing tool. This confirms that the measured transverse permeability can be significantly affected by the above mentioned factors.