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RISS 인기검색어
- 검색키워드
- 저자 : Engin Aktaş (검색결과 2 건)
- 무료
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Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by aramid nonwoven veils
Bertan Beylergil,Metin Tanoğlu,Engin Aktaş 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.2
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.
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Reliability of Corroded Steel Members Subjected to Elastic Lateral Torsional Buckling
Uzun Ertugrul Turker,Engin Aktaş 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4
Structural steel members are subjected to corrosion due to environmental condition. As a result, there is decreasing in the cross-section properties of the member. This causes diff erent stability problems and reduction in the load carrying capacity of members. Then, the probability of failure, P f increases due to corrosion. The need arises to determine expected level of safety for such members and systems. Besides, reliability of the steel structure is also eff ected by the structural stability problems that result decreasing in the resistance. Lateral torsional buckling is one of the most encountered problems in steel members and aff ected by the critical moment which is a function of lateral and torsional stiff ness. Critical moment depends on the material properties, boundary conditions, unbraced length, load pattern, and the member’s cross section. Under the corrosion, it is inevitable to observe changing in some of properties. In this study, a damage model to determine the reliability of a corroded I-shape steel member under linear moment gradient is developed considering corrosion exposure time. Uniform and varying thickness loss models are considered to show the corrosion eff ect. Infl uence of environmental condition on the load carrying capacity of the members is considered and their eff ects on member design is evaluated. As a result, it is concluded that load carrying capacity of steel members degrades and safety of them adversely eff ected. With presented formulas, it is ensured that the load carrying capacity and reliability indices of the steel members can be calculated practically under the examined situations
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