Effect of Gas Channel Design on Bending Properties of Gas-Assisted Injection Molded Polystyrene Parts

Abstract

Polystyrene (PS) thin plates designed with semicircular gas channel of different radius and with rectangular gas channel of different width to height ratio were gasassisted injection molded (GAIM). Effects of geometrical factors introduced by part thickness, various section shapes and the associated dimensions of gas channels on bending properties of GAIM parts were investigated via a bending test. It was found that gas channel design, introducing additional moment of inertia determined by the geometry of channel section and the hollowed core, results in part structural reinforcement. Bending properties of GAIM parts, including maximum bending load and absorbed bending energy, are enhanced when part thickness and the sizes of semicircular and rectangular gas channel increase. Part stiffness and maximum bending load increases linearly with inertia moment and section modulus of the plate, respectively. Increasing gas channel height has the best effect on the enhancement of bending stiffness. The present investigation provides part designers a guideline for choosing the most effective gas channel design to achieve a specific part bending structural performance.