Browsing by Author "Özmen, U"

Now showing 1 - 6 of 6
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    Thermal characterization of chicken feather/PLA biocomposites
    Özmen, U; Baba, BO
    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 delta 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.
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    Revealing the Long-term Ageing Effect on the Mechanical Properties of Chicken Feather Fibre/Poly(lactic acid) Biocomposites
    Akderya, T; Özmen, U; Baba, BO
    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.
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    Preparation and Mechanical Characterization of Chicken Feather/PLA Composites
    Baba, BO; Özmen, U
    Green composites, a bio-based polymer matrix is reinforced by natural fibers, are special class of biocomposites. 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. (C) 2015 Society of Plastics Engineers
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    PREDICTION OF THE ELASTIC MODULI OF CHICKEN-FEATHER-REINFORCED PLA AND A COMPARISON WITH EXPERIMENTAL RESULTS
    Özmen, U; Baba, BO
    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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    Computational Modeling of Functionally Graded Beams: A Novel Approach
    Özmen, U; Özhan, BB
    Aim A novel computational approach is propounded to model the material gradation of a functionally graded Euler-Bernoulli beam using Ansys Workbench, the finite element method-based software. Novelty Contrary to layer-by-layer modeling approaches to express functional material gradation for different structures in the literature, the new approach states a continuous variation of the material gradation obeying gradation laws (e.g., power-law). Method The new approach is applied to the computational free vibration analyses of functionally graded beams. Three types of functionally graded beams are investigated: (1) One-directional beam with a uniform cross section. (2) One-directional beam with a non-uniform cross section. (3) Bi-directional beam with a uniform cross section. Power-law and exponential-law types mathematical expressions are used in modeling the material gradation of functionally graded beams. Results The finite element results of free vibration analyses for each beam are obtained. The results are compared with the analytical results from the literature [Lee and Lee, Int J Mech Sci 122:1-17; Sinir et al., Compos Part B Eng 148:123-131; Karamanli, Anadolu Univ J Sci Technol A Appl Sci Eng haps://doi.org/10.18038/aubtda.361095; Simsek, Compos Struct 133:968-978] to present the accuracy of the novel approach. Several support conditions are investigated. The effects of the gradient indices (power-law and exponential-law indices) on the natural frequencies of the beams are discussed.
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    Investigation of long-term ageing effect on the thermal properties of chicken feather fibre/poly(lactic acid) biocomposites
    Akderya, T; Özmen, U; Baba, BO
    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.