Influence of back pressure and geometry on microstructure of injection-molded long-glass-fiber-reinforced polypropylene ribbed plates

Fiber-reinforced thermoplastic components are widely used in the automotive industry and are generally fabricated using injection molding. The mechanical properties of such components are critically dependent on the length and orientation of the fibers in the molded product. In this study, a plate with both transverse and longitudinal ribs across the entire surface is designed based on the concepts of the oil pan of vehicles. The novel injection molding machine is developed to have the capability to injection molding long-fiber-reinforced thermoplastic and maintain fiber length during the molding process. The study especially emphasizes the effects of back pressure, rib thickness, and plate thickness. The results show that the fiber length increases with a decreasing back pressure and an increasing plate thickness and rib thickness. The effect of the plate thickness on the fiber length is particularly significant. Moreover, the fiber orientation of the long-side and short-side rib is more in the flow direction.