The impact of pultrusion processing parameters on resin pressure rise inside a tapered cylindrical die for glass-fibre/epoxy composites

Pultrusion is a continuous process with application in the manufacture of fiber-reinforced composites. This work is focused on understanding the impact of various pultrusion process control parameters on the pressure-rise phenomenon inside a cylindrical die for glass-fibre/epoxy composites. The important process control parameters in pultrusion manufacturing are the pull speed, fiber volume fraction, viscosity, die heating zones temperature settings, and pre-form plate area ratio (compaction ratio). The pressure rise in the die inlet contributes to a major extent in enhancing fiber wet-out and suppressing void formation in the manufactured composite. A numerical model for evaluating the pressure-rise behavior inside the die inlet is developed on the basis of Darcyʹs law since the resin flow through the fibers is similar to the flow through porous media. A fixed control-volume-based finite-difference method known as the finite-volume method is employed to solve the governing equations of a three-dimensional axis-symmetric cylindrical die inlet geometry. Also, a variable viscosity model is used to compute the viscosity in the straight portion of the die.