Modelling and simulation of the pultrusion process with closed injection and impregnation molds

In this study, simulation models are developed for the physical processes occurring in pultrusion molds with closed injection and impregnation chambers. Two different mold inlet geometries are studied: a conical tapered inlet and a so called tear drop geometry. The modeled reaction is that of a two-step curing resin system. A commercial software package (Ansys CFX) is applied in the simulation studies. The flow of liquid resin in the injection and impregnation sections is calculated, resulting in predicted pressure and velocity fields within this region. The energy balance equations are solved for the porous (composite) and solid (heated die) domains, with an additional term for the heat generation due to the exothermic reaction. Solving the energy equations yields temperature and degree of cure fields within the die, which are used to calculate resin viscosity and volumetric changes due to thermal expansion and shrinkage due to curing. The pressure variation in the straight die section is obtained from the resin volumetric changes. Simulation results are compared to experimental data from pultrusion processing trials. Experimental data was also used to evaluate the fiber stack distribution within the tear drop die, which is necessary for defining porosity and permeability within the model.