Study of the Bending Properties in Gas-assisted Injection Molded Fiber-reinforced Nylon Parts

Glass fiber-reinforced Nylon plate parts designed with gas channels having five different types of cross section but with the same section were gas-assisted injection molded (GAIM). Effects of glass fiber content and geometrical factors introduced by various section shapes and the associated dimensions of gas channels on bending properties of GAIM parts were investigated via a bending test. Test results were also compared with those of conventional injection molded parts. Based on the measured results, it is found that gas-assisted injection molded parts show better bending properties including flexural strength, absorbed energy and bending stiffness than conventional injection molded parts. Alternatively, bending performance of GAIM parts increases when the content of glass fiber is increased. However, the fiber content of 15% has pretty good efficiency of bending performance. Meanwhile, for five gas channel designs, both gas channel designs attached with top rib (shapes D and E) show the higher bending stiffness and maximum bending load, correspondingly. So, generally speaking, these two gas channel designs provide the best enhancement in bending performance, however, parts with semicircular and rectangular gas channel designs (shapes A and B) can absorb more bending energy than the other designs. Alternatively, the flexural strength shows only slight influence from gas channel design, the deviation from average values less than 10%. The present study provides part designers with a design guideline for choosing the most effective gas channel design and fiber content to achieve a specific objective of part structural performance.