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    Improving bonding strength of injection overmolded composites
    (John Wiley and Sons Inc, 2022) Akpınar, Serkan; Metin, Merve; Koçoğlu, Hürol; Kodal, Mehmet; Sezen, Meltem; Özkoç, Güralp; Altan, M. Cengiz
    The overmolding of short fiber reinforced polymer compounds onto continuous fiber reinforced composite substrates provides design flexibility and the ability to tailor stiffness, strength, and damage tolerance for structural applications. In this work, a novel molding approach that enhances the bonding strength by mechanical interlocking is presented. The effectiveness of the proposed approach was validated by characterization of the bonding strength between a short glass fiber PP (SGFPP) composite overmolded onto a continuous glass fiber reinforced PP (CGFRPP) prepreg. Enhancement of the bonding strength was achieved by judiciously drilling tapered holes on the CGFRPP substrate before molding, which facilitated better interlocking with the injection molded SGFPP composite. The overmolding of preheated composites with tapered holes yielded up to 60% improvement in bonding strength. In general, having multiple holes helped improve bonding up to certain hole diameter. Similarly, preheating of the substrate over a short time improved the interfacial adhesion, while extended preheating resulted in a reduction of bonding quality. SEM analysis of the fracture surfaces after the tensile debonding test revealed that the SGFPP filled the holes on the substrate during overmolding. © 2022 Society of Plastics Engineers.
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    Investigation of effects of MoEpPOSS nanoparticle on the morphological and rheological properties of PA6/TPE blends
    (İdris Karagöz, 31 Temmuz 2024) Yıldırım, Rumeysa; Koçoğlu, Hürol; Ün, Merve; Ullah, Muhammad Saeed; Yakar, İpek; Ozkoc, Guralp; Mert, Olcay; Kodal, Mehmet
    Polyamide 6 (PA6) is one of the used engineering thermoplastics with the advantages of high resistance to chemicals and abrasion, high fatigue resistance and toughness. However, it has some disadvantages such as low impact strength and notch sensitivity. The blend of PA6 with elastomers can mitigate these shortcomings. Lately, thermoplastic elastomers (TPE) have been frequently used to toughen notch-sensitive polymers such as PA6 due to their outstanding properties such as high elasticity, recyclability, and easy processing. As it is known, obtaining superior properties in polymer blends relies on the interfacial interaction between the components of the blend. Additionally, by using compatibilizers, blends with the required properties can be created by enhancing interaction between phases, or interfacial adhesion. Recently, polyhedral oligomeric silsesquioxane (POSS) nanoparticles, organic/inorganic hybrid nanoparticles, are preferred as an alternative compatibilizer to conventional types. In this study, PA6/TPE blends were compatibilized with POSS nanoparticle with single epoxy group (MoEpPOSS). The morphological and rheological properties of PA6/TPE blends compatibilized with MoEpPOSS nanoparticle were investigated. Also, possible chemical interactions between PA6 and/or TPE and MoEpPOSS nanoparticle were determined via Fourier transform infrared spectroscopy (FTIR) analyses.
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    A new approach for the reuse of scrap carbon fiber in high-added value continuous fiber reinforced composite structures
    (Elsevier Ltd, 2022) Koçoğlu, Hürol; Kodal, Mehmet; Altan, M. Cengiz; Özçelik, Babür; Özkoç, Güralp
    This study proposes an innovative processing approach for high-added value hybrid fiber-reinforced composite structures by reusing scrap carbon fiber (CF). Thermoplastic prepregs were produced via wet-laid method using chopped polyamide 6.6 fibers as matrix and short scrap CFs as the reinforcing phase. These prepregs were then hot stacked with woven glass fabrics, forming a novel hybrid lightweight composite laminate. Silane treatment was used to improve the adhesion of glass fabric to the novel wet-laid scrap CF/PA6.6 prepregs. Tensile, flexural, dynamic-mechanical, and morphological properties of the composites were examined to characterize the effectiveness of the hybridization of short scrap CFs and glass fabric. The results showed that short scrap CF in the laminates increased the tensile strength up to 30 % and flexural strength up to 60 %. Moreover, silane surface modification of the glass fabric yielded a 140 % improvement in the flexural strength of scrap CF/PA6.6 prepreg-glass fabric hybrid laminates.