Civil Engineering / İnşaat Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/13

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Author: search.filters.author.Tanoğlu, MetinSubject: search.filters.subject.Delamination

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  • Article
    Citation - WoS: 39
    Citation - Scopus: 40
    Mode-I Fracture Toughness of Carbon Fiber/Epoxy Composites Interleaved by Aramid Nonwoven Veils
    (Techno Press, 2019) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, Engin
    In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m(2) to improve their Mode-I fracture toughness. The control and aramid interleaved CF/EP composite laminates were manufactured by VARTM in a [0]4 configuration. Tensile, three-point bending, compression, interlaminar shear, Charpy impact and Mode-I (DCB) fracture toughness values were determined to evaluate the effects of aramid nonwoven fabrics on the mechanical performance of the CF/EP composites. Thermomechanical behavior of the specimens was investigated by Dynamic Mechanical Analysis (DMA). The results showed that the propagation Mode-I fracture toughness values of CF/EP composites can be significantly improved (by about 72%) using aramid nonwoven fabrics. It was found that the main extrinsic toughening mechanism is aramid microfiber bridging acting behind the crack-tip. The incorporation of these nonwovens also increased interlaminar shear and Charpy impact strength by 10 and 16.5%, respectively. Moreover, it was revealed that the damping ability of the composites increased with the incorporation of aramid nonwoven fabrics in the interlaminar region of composites. On the other hand, they caused a reduction in in-plane mechanical properties due to the reduced carbon fiber volume fraction, increased thickness and void formation in the composites.
  • Article
    Citation - WoS: 97
    Citation - Scopus: 110
    Effect of Polyamide-6,6 (pa 66) Nonwoven Veils on the Mechanical Performance of Carbon Fiber/Epoxy Composites
    (Elsevier Ltd., 2018) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, Engin
    In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness.