Process simulation of LPM (Liquid Polymer Moulding) in special consideration of fluid velocity and viscosity characteristics

Recently in RTM process technique in-situ polymerizing thermoplastics are a promising alternative for conventional thermoset matrix systems. The advantages of these systems are a low initial viscosity at the beginning of the process combined with the polymerization proceeding during injection. The low initial viscosity allows a fast mold filling even at a high fiber volume fraction which leads to a high fluid velocity especially at the beginning of the process. Additionally, the polymerization during injection leads to a change not only of the viscosity level but also of the viscosity characteristic to a shear rate dependent behavior. The high flow velocity as well as the shear dependent viscosity do not allow to model this kind of process by the generally accepted Darcy's Law which assumes low flow velocity and newtonian viscosity of the fluid. The intention of this paper is to investigate a high velocity fluid flow in a non-crimp fiber bed as well as the influence of visco-elastic fluid characteristic on the fiber bed microstructure.