Abstract
In this study, we attempted to reduce mold wear in CFRTP injection molding by mixing long and short fiber pellets with different fiber lengths to reduce CF content and maintain strength. In addition, the internal structure of the molded specimens was visualized using CT scans to clarify the relationship between internal molding defects, CF distribution and orientation, CF length, and tensile strength. Tensile strength increased with increasing CF content in 100% short fiber. For 100% long fibers, the strength increased with CF content from 10wt% to 15wt%, but the strength decreased at 20wt% from 10wt%. At content rates of 10, 15, and 20 wt%, internal defects (voids) and uneven distribution of CF occur in long-fiber CFRTP at a content rate of 20 wt%, resulting in a decrease in strength. No internal defects or uneven CF distribution were observed in the short-fiber CFRTP at any content rate. By mixing 50wt% long-fiber pellets and 50wt% short-fiber pellets in the molding process, the same tensile strength as that of 100% short-fiber pellets with a CF content of 20wt% could be secured at a CF content of 15wt%. Therefore, it was clear that mixing pellets can reduce CF content and ensure strength. Factors that contributed to the maintenance of strength by pellet blending were that the CF distribution became uniform while suppressing the generation of defects such as voids, and that the fiber length inside the specimen became longer by mixing long fibers in addition to short fibers.
