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Steel and Composite Structures Volume 31, Number 2, April25 2019 , pages 113-123 DOI: https://doi.org/10.12989/scs.2019.31.2.113 |
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Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by aramid nonwoven veils |
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Bertan Beylergil, Metin Tanoğlu and Engin Aktaş
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| Abstract | ||
| In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with aramid nonwoven veils with an areal weight density of 8.5 g/m2 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. | ||
| Key Words | ||
| composite structures; crack; fiber reinforced polymers (FRPs); fracture/fracture criteria; delamination; bending and shear strength; axial compression | ||
| Address | ||
| (1) Bertan Beylergil: Department of Mechanical Engineering, Alanya Alaaddin Keykubat University, Alanya, Antalya, Turkey; (2) Bertan Beylergil, Metin Tanoğlu: Department of Mechanical Engineering, Izmir Institute of Technology, İzmir, Turkey; (3) Engin Aktaş: Department of Civil Engineering, Izmir Institute of Technology, Urla, İzmir, Turkey. | ||