Void transport in resin transfer molding

The transport of single drops through a hexagonal cylinder array is used to study the void movement and deformation in a resin transfer molding process. A transparent flow cell is used to visualize the transport of voids through a porous media model. Experiments are conducted with nearly inviscid water drops and viscous glycerol drops with drop sizes ranging from 0.4 to 80 μl, and with both a Newtonian fluid and Boger fluid with average resin velocities ranging from 0.011 to 0.140 cm/s. Two critical capillary numbers, which determine the breakup (Ca_b) and mobilization (Ca*) of drops, are measured to better understand the flow dynamics of voids. As demonstrated by the experiments, there is a critical drop size, below or above which a quite different flow behavior is observed. Such a transition is analyzed with consideration of the geometry characters in the flow field. Results expand the former studies in this area to a significantly larger range of drop sizes and capillary numbers. Particle Tracking Velocimetry is also used to quantify the local velocity, shear stress, extensional stress and energy dissipation in the flow field. Polym. Compos. 25:417–432, 2004. © 2004 Society of Plastics Engineers.