Effect of Rib Root Shape on the Rib Root Tensile Strength of Press and Injection Hybrid Molded Products Made with CF/PA6 Random Prepreg Sheet

Abstract

The hybrid molding method has been developed by combining press molding and injection molding to mold CFRTP with high-strength and high-stiffness for complex shaped products with ribs and bosses. In the hybrid molding, longer fibers such as continuous fibers and cut prepreg are used for the laminate of the press part and short fiber or long fiber pellets are used for the injection materials. It has been reported that the fracture occurs at the interface between the laminate and ribs. In our previous studies, to improve the rib root tensile strength, the supplying method of laminates to the rib structures was proposed. Since the rib root shape affects their flow behavior into the rib structure, it is necessary to clarify the influence of rib root shape on the rib root tensile strength. In this study, to clarify the effects of the molding pressure and rib root shape on the rib root tensile strength of the press and injection hybrid molded products, rib root tensile test of T-shaped specimens were conducted. CF/PA6 random prepreg sheets were used for the materials of the press part, and the molds with two kinds of radius of curvature R0 and R2.5 for rib root shape were used. Their fiber orientation and voids were evaluated by X-ray CT. Since the specimen with R0 has more carbon fibers oriented to the vertical direction to the interface than that with R2.5 at the press pressure of 8 MPa, the specimen with R0 had higher rib root tensile strength than that with R0. In terms of obtaining higher rib root tensile strength, R0 is the optimum rib root shape for the press and injection hybrid molded product.