Press and Injection Hybrid Molding Using CF/PP Unidirectional Slit Prepreg and Evaluation of Bonding Strength at Rib Root

Abstract

In the press and injection hybrid molding of CFRTP, short or long fiber-reinforced thermoplastics are injected on the continuous fiber-reinforced thermoplastics, which are used for the outer shell material. Since its fracture often occurs at a rib root portion, which is the interface of the injected materials and the continuous fiber-reinforced thermoplastics, the rib root portion has to be strengthened. By using slit material having high formability for the outer shell material, the penetration height of the outer shell material into the rib becomes higher, therefore, improvement of the strength of rib root portion can be expected. In this study, to clarify the effect of penetration height of slit materials on the mechanical properties of the rib root portion of the press and injection hybrid molding, slit materials were used for the outer shell material, and tensile tests of the surface layer and bonding strength at rib root were conducted. Experimental results reveal that the press and injection hybrid molding using slit materials in half of the continuous fiber-reinforced thermoplastics prepreg possesses the good combination of high bonding strength of rib root portion and high tensile strength of the surface layer.

Effects of the Injection Material and Resin Layer on the Mechanical Properties of Carbon Fiber-Reinforced Thermoplastic (CFRTP) Press and Injection Hybrid Molded Parts

“…As a result, P1C1 and P1C1G with a resin layer at the rib roots showed higher bond strengths than P0C1 and P0C1G without a resin layer. Previously, the authors reported that, in hybrid molding, the more the laminate flows into the ribs, the higher the bond strength is [12,13]. In this study, P0C2, which used 2 mm thick CFRTP laminates and did not have a resin layer, increased the bond strength due to the inflow into the ribs of the laminate.…”

“…The bond strength at the rib root of each hat-shaped part was evaluated by a tensile test using a universal testing instrument (5566, Instron, Norwood, MA, USA) with a T-shaped specimen cut out, as shown in Figure 4. With reference to the previous studies [12,13,20], T-shaped tensile tests were conducted. T-shaped tensile tests were also performed on specimens of P1C1 and P1C1G in which the resin layer at the rib root was removed using abrasive paper, as shown in Figure 5.…”

“…A method to prevent interfacial failure between the surface material and the ribs is one that the CFRTP laminate penetrates into the ribs. The authors have developed a method to improve bond strength by supplying either cut or slit materials of a continuous fiber prepreg that has excellent flowability at the bonding area [12,13]. However, there is concern that the end of the fiber bundle in the cut material and the cut portion in the slit material may be the starting point of failure [14].…”

Effect of Rib Root Shape on the Tensile Strength of Press and Injection Hybrid Molded Products Made With Cf/Pa6 Random Prepreg Sheet

“…7(b) is lower than the tensile strength of PA6. We reported that the oriented discontinuous fiber in the rib to vertical direction to the interface contributed the improvement of the interfacial strength [6], [7]. Fiber orientation at the interface between the laminates and injected materials is considered to be the reason for the difference of rib root tensile strength and fracture surface.…”

“…In our previous study, it has been reported that fracture occurs at the interface between laminates and ribs for the press and injection hybrid molding [5]. To improve the interfacial strength, supplying method of discontinuous fibers to the interface between laminates and ribs was proposed, and the oriented discontinuous fiber in the rib to vertical direction to the interface contributed the improvement of the interfacial strength [6], [7]. Although rib root shape or radius of curvature is the important factor in the press and injection hybrid molding, the effect of rib root shape on the mechanical property has not been clarified yet.…”