Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article A Steel-Reinforced Recycled Thermoplastic Composite for Wind Turbine Towers: Experimental and Full-Scale Validation(MDPI, 2026) Ciftci, Cihan; Altikaya, Hasan TolgaThe increasing demand for sustainable and lightweight structural systems has motivated the development of alternative materials for wind turbine tower applications, where conventional steel structures are associated with high material consumption and environmental impact. In this study, a novel steel-reinforced recycled thermoplastic composite system is proposed as an alternative structural solution. To enable the design and practical application of such composite systems, the mechanical properties of the recycled thermoplastic matrix were experimentally characterized. Compression and tensile tests revealed average yield strengths of approximately 32 MPa in compression and 7.8 MPa in tension. To account for the environmental conditions encountered in field applications, the temperature-dependent mechanical behavior of the material was investigated. Since the critical mechanical response of the thermoplastic matrix in the composite system is governed by compression rather than tension, the study was limited to compression tests under elevated temperatures. The results show that the compressive yield strength decreases to approximately 31 MPa at 55 degrees C. An analytical model based on the transformed-section approach was also developed to predict the flexural behavior of the composite section and was validated through three-point bending tests, with an analytically predicted yield load of approximately 31.5 kN showing good agreement with experimental results. To assess structural applicability at a larger scale, a full-scale composite wind turbine tower was designed and manufactured, and its dynamic performance was evaluated through field measurements under natural wind loading conditions. The results indicate that the composite tower exhibits comparable dynamic behavior to a conventional steel tower, with a first natural frequency of approximately 3.08 Hz compared to 2.89 Hz for the steel tower, along with enhanced damping characteristics. These findings demonstrate that steel-reinforced recycled thermoplastic composites offer a promising and sustainable alternative for wind turbine tower applications, with potential for broader use in structural systems.Article Citation - WoS: 11Citation - Scopus: 12Investigation of the Mechanical Behavior of a New Generation Wind Turbine Blade Technology(MDPI, 2023-02-16) Ciftci, Cihan; Erdogan, Ayse; Genc, Mustafa SerdarWind turbine blades are one of the largest parts of wind power systems. It is a handicap that these large parts of numerous wind turbines will become scrap in the near future. To prevent this handicap, newly produced blades should be recyclable. In this study, a turbine blade, known as the new generation of turbine blade, was manufactured with reinforced carbon beams and recycled, low-density polyethylene materials. The manufacturing addressed in this study reveals two novelties: (1) it produces a heterogeneous turbine blade; and (2) it produces a recyclable blade. In addition, this study also covers mechanical tests using a digital image correlation (DIC) system and modeling investigations of the new generation blade. For the mechanical tests, displacement and strain data of both new generation and conventional commercial blades were measured by the DIC method. Instead of dealing with the modeling difficulty of the new generation blade's heterogeneity we modeled the blade structural system as a whole using the moment-curvature method as part of the finite element method. Then, the behavior of both the new generation and commercial blades at varying wind speeds and different angles of attack were compared. Consequently, the data reveal that the new generation blades performed sufficiently well compared with commercial blades regarding their stiffness.Article Citation - WoS: 35Citation - Scopus: 41Analysis of the Probability of Failure for Open-Grown Trees During Wind Storms(Elsevier Sci Ltd, 2014-07) Ciftci, Cihan; Arwade, Sanjay R.; Kane, Brian; Brena, Sergio F.Although trees convey important environmental, economic, and sociological benefits on humans and society, they can also cause significant economic and societal disruptions, especially when subjected to wind storms in urban environments. Tools for proper assessment of the risk of these disruptions can be of significant benefit to society. In this research an approach to quantifying the failure probability for trees subject to wind storms is presented and illustrated by application to two specific maple trees in Massachusetts, USA. The approach entails four specific steps: (-1) Random wind time history samples were generated using a modified Ochi-Shin spectrum, (2) these wind time histories were used as loading time histories on finite element models of the example trees in both summer (in-leaf) and winter (leafless), (3) maximum bending moments generated by the random wind time histories were compared to the failure (yield) moment of the tree at 1.4 m above ground, (4) the failure/fragility curves of the trees were estimated by Monte Carlo simulation for a range of average wind speeds and for 1000 independent wind time histories at each wind speed. (C) 2014 Elsevier Ltd. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 6A Rational Utilization of Reinforcement Material for Flexural Design of 3D-Printed Composite Beams(Sage Publications Ltd, 2019-08-05) Ciftci, Cihan; Sas, Hatice S.Recent developments in composite industry address the adaptation of 3D printing technology to overcome the design and manufacturing challenges of the traditional composite processing techniques. This adaptation can be performed with the development of design methodologies corresponding to the type of structural load-carrying members in a structure. Considering the frequently use of beams in structures, the development of the design methodology of beams is essential for the adaptation of the additive manufacturing. Therefore, in this paper, the flexural loading concept is analytically formulated to derive moment capacity for the flexural behavior of 3D-printed composite beams. Then, the formulation is adapted to develop a design methodology of 3D-printed laminates under flexural loading. Additionally, the analytical solutions developed for the design methodology presented in this paper were verified with a good agreement with experimental studies.Article A rational utilization of reinforcement material for flexural design of 3D-printed composite beams(SAGE PUBLICATIONS LTD, 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND, 2019) Ciftci, Cihan; Sas, Hatice S.Recent developments in composite industry address the adaptation of 3D printing technology to overcome the design and manufacturing challenges of the traditional composite processing techniques. This adaptation can be performed with the development of design methodologies corresponding to the type of structural load-carrying members in a structure. Considering the frequently use of beams in structures, the development of the design methodology of beams is essential for the adaptation of the additive manufacturing. Therefore, in this paper, the flexural loading concept is analytically formulated to derive moment capacity for the flexural behavior of 3D-printed composite beams. Then, the formulation is adapted to develop a design methodology of 3D-printed laminates under flexural loading. Additionally, the analytical solutions developed for the design methodology presented in this paper were verified with a good agreement with experimental studies.