THE STIFFNESS AND STRENGTH OF GAS-ASSISTED RIBBED PARTS : THE EFFECT OF GAS CORE SIZE AND ITS PREDICTION

摘要

The structural performance of a gas-assisted injection molded part will be influenced by the size and location of its hollow gas core. Experiments are performed to quantitatively assess the effect of gas core size on part stiffness and strength and a simple methodology is proposed and evaluated for predicting the size of the gas core prior to part fabrication. Three-point-bend tests are performed on two gas-assisted ribbed-plaque geometries for two resins, polycarbonate and polybutylene terephalate. Variations in part stiffness and strength are measured and correlated with variations in gas core size. The methodology for predicting gas core size is evaluated by comparing finite element results using the predicted gas core dimensions to finite element results using measured gas core dimensions and to actual experimental data. The simple prediction methodology agrees well with experimental results, provided the gas doesn't penetrate from the rib into the surrounding plate.