Investigation of the pressure behavior in a pultrusion die for graphite/epoxy composites

There are a variety of ways to process composite materials. One such way is pultrusion which is a continuous process for manufacturing composite materials of constant cross-sections. The pultrusion process involves a number of variables and processing parameters which can affect the quality of a pultruded product. One variable of particular interest is the fluid resin pressure rise in the tapered inlet region of the die. The liquid resin pressure rise in the die inlet can have a significant impact on the quality of a pultruded product. An appreciable pressure rise can suppress void formations and enhance fiber “wet out”. Darcy’s law for flow in a porous media is used to mathematically model the fiber/resin system of the pultrusion process, while employing the finite volume solution method to predict the pressure and velocity fields as a function of various process control parameters. The results obtained by the numerical model can establish a foundation by which process control parameters are selected to achieve an appreciable pressure rise which will enhance the quality of the pultruded composite. The results can also be applied to die inlet design.