EFFECTS OF PULL SPEED ON DIE WALL TEMPERATURES FOR FLAT COMPOSITES OFVARIOUS SIZES

Properties of pultruded composites depend strongly on processing varia bles such as pull speed. Die wall temperatures may change depending on the size of the composite and the pull speed due to heat absorption o r heat generation by the composite. It is the objective of this study to emphasize the importance of predicting and understanding the impact of die wall temperatures on centerline temperatures and degree of cur e for composites of various thicknesses pultruded at different pull sp eeds. In order to accomplish this goal, a transient, three-dimensional numerical thermochemical heat transfer model for the heating section of the pultruder was developed. The governing energy and species equat ions for the composite were solved using a finite difference control v olume scheme. The kinetic parameters for Shell EPON 9420 epoxy resin, determined using a heat flux type differential scanning calorimeter (D SC), were employed in this study. Previous researchers have tended to ignore the variations in die wall temperature distribution or have rel ied on experimentally obtained die wall temperature data to develop mo dels and make predictions. This research overcomes those restrictions by completely predicting the temperature profiles in the entire die, t hereby providing the pultrusion engineer with the tools to design a he ating section of a pultrusion machine. An operational envelope has als o been developed to establish guidelines for maximum pull speeds that can be used to obtain a specified degree of cure in the composite.