Hydrodynamically induced preform deformation

Abstract Large pressure gradients developed in high‐speed liquid composite molding may produce hydrodynamically induced preform deformation. Such deformation 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 conditions where preform deformation is expected to play a dominant role during mold filling. The model includes preform material properties such as stiffness, permeability, and clamping pressure, as well as the process injection pressure and the mold geometry. The utility of the model is illustrated for two reinforcement materials, a random mat and a 3‐dimensional woven fabric.