HYDRODYNAMICALLY INDUCED PREFORM DEFORMATION

Large pressure gradients developed in high-speed liquid composite mold ing may produce hydrodynamically induced preform deformation. Such def ormation away from the mold wall is expected to open new flow channels , creating edge effects and rendering mold filling calculations based on Darcy's law inaccurate. A simple model is proposed to assess the co nditions where preform deformation is expected to play a dominant role during mold filling. The model includes preform material properties s uch as stiffness, permeability, and clamping pressure, as well as the process injection pressure and the mold geometry. The utility of the m odel is illustrated for two reinforcement materials, a random mat and a 3-dimensional woven fabric.