The Low Breaking Fiber Mechanism and Its Effect on the Behavior of the Melt Flow of Injection Molded Ultra-Long Glass Fiber Reinforced Polypropylene Composites

Abstract

In this study, fiber breaking behavior, fiber orientation, length variation, and changes in melt flow ability of long glass fiber reinforced polypropylene (L-FRP) composites under different mold cavity geometry, melt fill path, and plasticization parameters were investigated. The matrix material used was polypropylene and the reinforcement fibers were 25 mm long. An ultra-long-fiber composite injection molding machine (with a three-stage plunger and injection mechanism design) was used with different mold cavity geometry and plasticization parameters. Different screw speeds were used to explore the changes in fiber length and to provide a reference for setting fiber length and parameter combinations. Flow-length specimen molds with different specimen thickness, melt fill path, and gate design were used to observe the effect of plasticizing properties on the flow ability of the L-FRP composite materials. The experimental results showed that the use of an injection molding machine with a mechanism that reduced the amount of fiber breakage was advantageous. It was also found that an increase in screw speed increased fiber breakage, and 25 mm long fibers were shortened by an average of 50% (to 10 mm). Long fibers were more resistant to melt filling than short fibers. In addition, the thickness of the specimen and the gate design were also found to affect the filling process. The rounded angle gate and thick wall product decreased the flow resistance and assisted the flow ability and fiber distribution of the L-FRP injection molding.

Fabrication and Property Characterization of Long-Glass-Fiber-Reinforced Polypropylene Composites Processed Using a Three-Barrel Injection Molding Machine

“…However, as shown in Figure 10 c, the melt temperature had almost no effect on the fiber length. The result is similar to that of the previous research by Huang et al [ 26 ].…”

Investigation of the Fiber Length and the Mechanical Properties of Waste Recycled from Continuous Glass Fiber-Reinforced Polypropylene

“…In injection molding, the plasticizing process is affected by screw speed, processing temperature, and back pressure. Meanwhile, the injection process is determined by component geometry, injection speed, and holding pressure [23,31,32]. External factors such as contamination, processing errors, and ambient temperature also play a crucial role.…”

“…Additionally, Huang, Peng, and Hwang investigated the fracture behavior and fiber length distribution of polypropylene with glass fibers during injection molding, utilizing glass fibers with a length of 25 mm. They found that increasing the screw speed contributed to the shortening of the reinforcing fibers [32]. Furthermore, Goris, Back, and Yanev studied the influence of screw speed in addition to back pressure.…”

The influence of tool’s surface topography on mechanical properties of injection moulded product

“…Furthermore, research papers [3][4][5][6] investigated the influence of other process parameters, specifically pressure and temperature, on final flow length. The influence of process parameters was also investigated in publications [7][8][9]. And finally, following published papers [10][11][12] investigated various effects of process parameters, for example pressure and melt flow index, or the reason for the creation of flow marks.…”