Effect of Fiber Content of Injection Material on Mechanical Properties of Melted Thermoplastic-Resin Transfer Molded Products

Abstract

The weight reduction of a vehicle body is expected by applying FRTP (Fiber Reinforced Thermoplastics), which have excellent mechanical properties of high specific strength and high specific stiffness. When molding structual parts of FRTP,press and injection hybrid molding is used, in which after preheated continuous fiber reinforced laminates is shaped into a complex shell shaped structure, such as ribs and bosses are added by injection molding. FRTP parts manufactured by hybrid molding often fracture at the interface between continuous fiber reinforced laminates and the injected material, thus a method for improving the strength of the rib root part is required. We have been developing the MT-RTM (Melted Thermoplastic-Resin Transfer Molding) method, which applies the RTM (Resin Transfer Molding) method to thermoplastic resins. For MT-RTM molded products, high interfacial strength can be expected, as the injected materials will be the matrix of continuous fiber reinforces laminates and no welds at the interface occurred. In this study, MT-RTM molding was applied to the hybrid molding, and the tensile test of the shell part and rib part using fiber reinforced thermoplastic resin with different fiber content as the injection material were carried out, the effect of fiber content of injection material on mechanical properties was clarified. When thermoplastic resin is injected and molded, the resin was easily impregnated into the glass fiber plain woven fabric, molded products with low porosity and high tensile strength was obtained. When a short glass fiber reinforced thermoplastic is used as an injection material for MT-RTM, the resin impregnated into the fabrics and some short glass fibers would also penetrate into tthe fabrics. The appropriate fiber content of the injection material used within our study is 20 wt%, and by using PP with MAPP, the wettability and interfacial adhesive strength are improved; and FRTP with high tensile strength is molded in the shell part and rib root part.