Effect of Thickness on Weld Line Strength of Injection Molded Thermoplastic Composites

Abstract

The injection molding of thermoplastic composites has become an important process, especially in the automotive industry, due to high-volume production rates and their ability to be molded into complex shapes. However, there are still several unresolved problems that confound the overall success of this technology. Among them, weld lines are the most prevalent, occurring in most injection-molded parts, except those with very simple geometry. The formation of a weld line is regarded as one of the most undesirable phenomena, especially in injection-molded, fiber-reinforced thermoplastics, since it may result in poor appearance as well as poor mechanical properties. The focus of this study was to determine the effect of component thickness on the weld line strength of injection-molded, short-fiberreinforced, thermoplastic composites. Comparisons were also made with injection-molded parts without weld lines. The use of design data, which take into account fiber orientation as well as thickness, will enable design engineers to predict more accurately the performance of a molded part under applied load.