Evaluation of Mechanical Properties of Glass Fiber Reinforced Polypropylene Composites Made by Press and Injection Hybrid Molding

Abstract

In the press and injection hybrid molding of GFRTP, short or long fiber reinforced thermoplastics or thermoplastics are injected on the continuous fiber reinforced thermoplastics, which allows us to obtain light weight structures with excellent strength and stiffness. In previous studies, it has been reported that the interfacial bonding strength between laminates and ribs was improved by supplying fiber of laminates to the interface. Although the interfacial bonding strength of the hybrid molded product was improved, its fracture occurred at the injected material or the interface between laminates and ribs. In the case of the fracture at the injected material, it is expected to improve the interfacial bonding strength by using fiber reinforced thermoplastic with higher mechanical properties as injection material. For the injection molding, forming a V-shaped interface by moving the melted resin was reported to improve the weld strength. This technique can be applied to the press and injection hybrid molding and may improve the interfacial bonding strength. In this study, GFRTP were molded by press and injection hybrid molding under different injection volumes using PP and the short glass fiber reinforced thermoplastics and the effect of injection material and injection volumes on the interfacial bonding strength was clarified by the tensile tests using T-shaped specimens cut out from the molded products. When larger volume of the short fiber reinforced thermoplastics was injected, fracture occurred mostly at the injected material and higher interfacial bonding strength was obtained.