PSI - Issue 45

Quan Jiang et al. / Procedia Structural Integrity 45 (2023) 117–124 / Structural Integrity Procedia 00 (2022) 000 – 000

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metal and ceramic, but they have valuable material properties. Impact strength is emphasized for SGFRTPs used in the scenarios described above. The impact resistance of SGFRTPs injection-molded products is also often evaluated according to the notched impact strength. Chang et al. (2021) reported that SGFRTP strength and impact resistance are governed by factors originating from the fiber, the matrix, and the interface between the fiber and the matrix. Among the factors originating from the fiber – matrix interface, interfacial shear strength (IFSS) has attracted attention as strongly affecting the mechanical properties of fiber-reinforced plastics. In recent years, studies of IFSS and impact strength have been very active. Many reports have described a positive correlation between these properties (Kallel et al., 2018). Nevertheless, no quantitative relation has been defined clearly. In fact, IFSS have been evaluated using numerous methods: pull-out by Zarges et al. (2017), push-out by To et al. (2015), fragmentation by Mahato et al. (2020) and T. Irisawa et al. (2017), and pinhole pull-out methods by M. Kanai et al. (2021). Although these methods are fundamentally effective for assessing the fiber – matrix interface, they are inapplicable to actual molded products because they require the preparation of special molded products for evaluation. Given this background, we proposed a method to obtain the IFSS by short beam shear testing using SGFRTPs injection-molded products. This method enables the evaluation of IFSS using molded products. Correlation between IFSS and mechanical properties such as strength and toughness can be derived quantitatively. For this study, correlation between the notched impact strength and IFSS calculated using the short beam test was clarified for SGFRTP injection-molded products. Then the model was validated by comparison of estimated results with experimentally obtained results. 2. Materials and Sample Preparations 2.1. Materials Polypropylene (PP, Novatec MA1B; Japan Polypropylene Corp.) and polystyrene (PS, Toyo Styrene GPPS G210C; Toyo-Styrene Co., Ltd.) were used as matrices. Glass fibers (GF, ECS 03 T351; Nippon Electric Glass Co., Ltd.) that had been surface-modified with amino groups were used as fibers. Polypropylene maleic anhydride (MAHPP, SCONA TSPP10213; BYK Additives & Instruments Co. Ltd.) and polystyrene maleic anhydride (MAHPS, RESISFY R200; Denka Co. Ltd.) were used as additives. 2.2. Sample preparations These materials were filled into a twin-screw extruder (IMC0-00; Imoto Machinery Co., Ltd.) and were melt-mixed at the injection temperature of 230°C, with screw speed of 60 rpm. A 15-mm-diameter screw was installed in the extruder. The ratio of screw length to the screw diameter is 25. The GF content was fixed at 30 wt%. Also, MAHPP and MAHPS contents were fixed at 5 wt%. The melt-kneaded strands were pelletized using a pelletizer (cold-cut pelletizer; Toyo Seiki Co., Ltd.) to obtain 3-mm-long composite pellets. The obtained composite material pellets were filled into a micro electric injection molding machine (C, Mobile0813; Shinko Sellbic Co., Ltd.) and were injection-molded to obtain beam-shaped molded products with injection temperature of 230°C and mold temperature of 50°C. The injection conditions of PP/GF and PP/ MAHPP/GF at the injection speed of 30 mm/s and at 56 MPa holding pressure. The injection conditions of PS/GF and PS/MAHPP/GF included injection speed of 20 mm/s and holding pressure of 70 MPa. The GF contents of all matrices were controlled to 10, 20, and 30 wt%. This machine uses a pre-plunger system with a 10-mm-diameter plunger and 29.4 kN mold clamping pressure. The mold cavity shape and the obtained beam-shaped molded product dimension are shown in Figures 1(a) and 1(b). The molded product thickness was 2 mm.

Fig. 1. (a) Mold cavity shape; (b) Beam-shaped molded product dimension.