Browsing by Author "Baba B.O."

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    Impact response of sandwich beams with various curvatures and debonds
    (2013) Baba B.O.
    This article presents experimental results of the impact response and failure characteristics of curved composite sandwich beam with debond. The objective of this study is to determine how the curvature and debond affects the contact force, displacement, absorbed energy, and damage type under impact loading. An instrumented drop-weight impact test are performed on sandwich beams made of carbon/epoxy face sheets and polyurethane foam core material with four different radii of curvature and debonds between the top and bottom interface of face sheet and foam core. Impact energy was kept constant of 4 J. The contact force and displacement histories of curved sandwich composites with debond are measured to determine the impact response. The results are compared with those of flat beams with the same dimensions and no debond. They indicate that the value of the contact force increases as the curvature angle increases for the beam with no debond. Opposed to the beams with no debond, the contact force decreases as the curvature angle increases for the beam with debond. These results show that curvature angle and debond are important mechanical parameters that must be considered in the design of structures. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
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    Prediction of the elastic moduli of chicken-feather-reinforced pla and a comparison with experimental results
    (Institute of Metals Technology, 2016) Özmen U.; Baba B.O.
    The purpose of this study is to obtain the elastic moduli, the key material property, of random discontinuous fiber composites with experiments and micromechanical models and to compare them. The proposed study makes it possible to assess the elastic moduli of chicken-feather fiber (CFF)/PLA green composites with different CFF mass fractions and to determine the feasibility of the micromechanical models for the CFF/PLA composites. For this purpose, initially, CFF/PLA composites including 2, 5 or 10 % chicken-feather mass fractions were extruded and standard tensile specimens for ISO 527 were formed with the injection-molding method. Tensile tests were carried out in accordance with the standards and the elastic moduli were calculated using the stress-strain curve. Then, using six different micromechanical models, the elastic moduli of the CFF/PLA composites with different mass fractions were calculated and compared with the experimental results. The results of the experiments and the models indicated that the presence of chicken feather increased the elastic moduli of all the composites in comparison with the pure PLA. According to the experimental data, the maximum increase in the elastic moduli of the composites with the presence of CFF was found to be 5.4 %. The maximum error in the prediction is about 16.8 % for the composite with a chicken-feather rate of 10 % when Manera's model is used. Among the micromechanical models, the ones that gave more converging results for the prediction of the elastic moduli of the CFF/PLA composites are Pan's 2-D, IROM (the inverse rule of mixtures), Nielsen-Chen and Halpin-Tsai models. A comparison of the results of these six models shows that the maximum deviation (the percentage error in prediction) is the smallest (1.4 %) for the Nielsen-Chen model. Therefore, the Nielsen-Chen model is the most appropriate model for the prediction of the elastic moduli of the CFF/PLA composites.
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    The effect of curvature on the impact response of foam-based sandwich composite panels
    (Techno Press, 2016) Yurddaskal M.; Baba B.O.
    The aim of this study is to investigate the impact behavior and impact-induced damage of sandwich composites made of E-glass/epoxy face sheets and PVC foam. The studies were carried out on square flat and curved sandwich panels with two different radius of curvatures. Impact tests were performed under impact energies of 10 J, 25 J and 80 J using an instrumented drop-weight machine. Contact force and displacement versus time and contact force-displacement graphs of sandwich panels were presented to determine the panel response. Through these graphs, the energy absorbing capacity of the sandwich panels was determined. The impact responses and failure modes of flat and curved sandwich panels were compared and the effect of curvature on sandwich composite panel was demonstrated. Testing has shown that the maximum contact force decrease while displacement increases with increasing of panel curvature and curved panels exhibits mixed failure mode, with cylindrical and cone cracking. Copyright © 2016 Techno-Press, Ltd.
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    Thermal characterization of chicken feather/PLA biocomposites
    (Springer Science and Business Media B.V., 2017) Özmen U.; Baba B.O.
    In this work, thermal properties of composites from chicken feather fiber (CFF) and polylactic acid (PLA) were investigated. CFF/PLA green composites were manufactured by extrusion and injection molding. Short and long fibers (3 and 20 mm) were used at different contents (2, 5 and 10 mass%). The effects of fiber concentration and fiber length on thermal properties of CFF/PLA composites were studied. Thermal properties of CFF/PLA composites were examined through differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and dynamic mechanical analysis (DMA). From the experiments, it was found that addition of CFF was effective to improve the thermal properties of PLA. The DSC results showed that heat flow increased with the increase in CFF content on the glass transition, on the crystallization temperature and on melting temperature. The TG results revealed that addition of CFF to PLA had positive effect on the thermal stability. In addition, the results of DMA experiments showed that the tan δ decreased with the increasing CFF content, indicating less damping and more elastic behavior in the composites. The results obtained from this study provide important information on the temperature-dependent properties of CFF/PLA and lead to new product development based on natural resources. © 2017, Akadémiai Kiadó, Budapest, Hungary.
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    Preparation and mechanical characterization of chicken feather/PLA composites
    (John Wiley and Sons Inc., 2017) Baba B.O.; Özmen U.
    Green composites, a bio-based polymer matrix is reinforced by natural fibers, are special class of bio-composites. Interest about green composites is continuously growing because they are environment-friendly. This study describes the preparation and mechanical characterization of green composites using polylactic acid (PLA) matrix including chicken feather fiber (CFF) as reinforcement. Extrusion and an injection molding process were used to prepare CFF/PLA composites at a controlled temperature range. CFF/PLA composites with fiber mass content of 2%, 5%, and 10% were manufactured. The effects of fiber concentration and fiber length on mechanical properties of CFF/PLA composites have been studied. Mechanical properties of composites were investigated by tensile, compression, bending, hardness, and Izod impact testing. The results of experiments indicated that Young's modulus, compressive strength, flexural modulus, and hardness of the PLA reinforced CFF composites are higher but tensile strength, elongation at break, bending strength and impact strength of them are lower than pure PLA. The results indicate that these types of composites can be used for various applications. POLYM. COMPOS., 38:837–845, 2017. © 2015 Society of Plastics Engineers. © 2015 Society of Plastics Engineers
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    Investigation of long-term ageing effect on the thermal properties of chicken feather fibre/poly(lactic acid) biocomposites
    (Springer, 2020) Akderya T.; Özmen U.; Baba B.O.
    In this study, the effects of long-term natural atmospheric ageing on the thermal properties of chicken feather fibre reinforced poly(lactic acid) biocomposite materials having chicken feather fibre mass content of 2, 5, and 10% were investigated. Chicken feather fibres, which are bio-based reinforcement material, and poly(lactic acid), which is bio-based matrix material, are compounded with a twin-screw extruder and injection-moulded; hence, the biocomposite material is produced. The effect of long-term natural atmospheric ageing on the thermal stability, crystallization, and melting behaviour of the biocomposite materials were analysed by thermogravimetric, derivative thermogravimetry, differential thermal, and differential scanning calorimetry analyses. In addition, the fracture surface of the samples was examined in depth by scanning electron microscopy analysis. The experimental results show that the long-term natural ageing process decreases the thermal stability values of the biocomposite materials and increases the glass transition temperatures and degree of crystallinities. © 2020, The Polymer Society, Taipei.
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    Revealing the Long-term Ageing Effect on the Mechanical Properties of Chicken Feather Fibre/Poly(lactic acid) Biocomposites
    (Korean Fiber Society, 2021) Akderya T.; Özmen U.; Baba B.O.
    Recently, bio-based polymer composites have been preferred instead of petroleum-based polymer composites due to increased sensitivity, awareness, and interest level in the fields of depletion of oil resources and environmental pollution. These eco-friendly materials, also called green composites, are reinforced with natural fibres and have superior properties such as biodegradability. In this paper, the effect of long-term ageing on mechanical properties of biocomposite material containing chicken feather fibre (CFF) as additive and poly(lactic acid) (PLA) as matrix is studied. The mechanical properties of pure PLA and CFF/PLA biocomposites, which are gradually increasing in mass concentrations of 2 %, 5 % and 10 %, have been investigated by tensile, compressive and hardness tests, and also the fracture surfaces were examined by SEM micrographs. The experimental results show that the long-term ageing effect causes the mechanical properties of pure PLA and CFF/PLA biocomposites to decrease. The lowest values of mechanical properties are found in the 5 % and 10 % CFF/PLA biocomposite materials that have the highest mass concentration of CFF. © 2021, The Korean Fiber Society for Fibers and Polymers and Springer.
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    A micromechanical approach to elastic modulus of long-term aged chicken feather fibre/poly(lactic acid) biocomposites
    (Walter de Gruyter GmbH, 2022) Akderya T.; Ozmen U.; Baba B.O.
    The modulus of elasticity is a critical parameter for the performance design and analysis of biofibre-based biocomposite materials. As a result of criteria such as internal heterogeneity, the random distribution of fibres and the success of interfacial adhesion between the fibre and the matrix, it becomes difficult to predict the modulus of elasticity in practical ways. Therefore, one of the aims of this study is to determine the modulus of elasticity of biocomposite material reinforced with discontinuous and random fibres by means of micromechanical models and experimentally. In addition, it is also aimed to reveal which micromechanical model can be used reliably in predicting the modulus of elasticity of both aged and non-aged biocomposite materials due to the relationship between the analytical and experimental results. In order to achieve these objectives, initially, chicken feather fibre/poly (lactic acid) biocomposite specimens having 2, 5 and 10 % chicken feather fibre mass fractions were mixed and manufactured by extruding, and subsequently, tensile test specimens according to the appropriate standard were formed by the injection-moulding method. An agreement between the moduli of elasticity obtained from 6 micromechanical models and experimentally from the slope of the stress-strain curves resulting from tensile tests was determined. © 2022 Walter de Gruyter GmbH, Berlin/Boston.