Fast liquid composite molding simulation of unsaturated flow in dual‐scale fiber mats using the imbibition characteristics of a fabric‐based unit cell

The use of the dual‐scale fiber mats in liquid composite molding (LCM) process for making composites parts gives rise to the unsaturated flow during the mold‐filling process. The usual approaches for modeling such flows involve using a sink term in the mass balance equation along with the Darcy's law. Sink functions involving complex microflows inside tows with realistic tow geometries have not been attempted in the past because of the problem of high computational costs arising from the coupling of the macroscopic gap flows with the microscopic tow flows. In this study, a new “lumped” sink function is proposed for the isothermal flow simulation, which is a function of the gap pressure, capillary pressure, and tow saturation, and which is estimated without solving for the microscopic tow simulations at each node of the FE mesh in the finite element/control volume algorithm. The sink function is calibrated with the help of the tow microflow simulation in a stand‐alone unit cell of the dual‐scale fiber mat. This new approach, which does not use any fitting parameters, achieved a good validation against a previous published result on the 1D unsaturated flow in a biaxial stitched mat—satisfactory comparisons of the inlet‐pressure history as well as the saturation distributions were achieved. Finally, the unsaturated flow is studied in a car hood‐type LCM mold geometry using the code PORE‐FLOW© based on the proposed algorithm. POLYM. COMPOS., 31:1790–1807, 2010.