Yazar "Yildiz, Mehmet" seçeneğine göre listele

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    A rational study on the hydrothermal aging of AFP manufactured CF/polyetherketoneketone composites with in situ consolidation supported by acoustic emission inspection
    (Wiley, 2022) Sukur, Emine Feyza; Elmas, Sinem; Seyyednourani, Mahsa; Eskizeybek, Volkan; Yildiz, Mehmet; Sas, Hatice S.
    In this study, carbon fiber (CF)/polyetherketoneketone (PEKK) composites with 5% void content, manufactured via an in situ consolidated automated fiber placement (AFP) lay-up process, are aged in hot water at 70 degrees C for 30 days. Firstly, a deep understanding of the deterioration in the mechanical performance is developed with a comprehensive and complementary set of material characterization strategies, including (i) microstructural characterization with Fourier-transform infrared spectroscopy (FTIR), (ii) thermal characterization with differential scanning calorimetry (DSC), and (iii) dynamic mechanical analysis (DMA). The material characterization concurrently highlights the plasticization and post-crystallization phenomena after aging with changes in the peak densities with FTIR, formation of second glass transition temperature (T-g) in DSC and DMA, and drop in storage modulus, loss modulus, and tan delta (delta) amplitudes. Then, acoustic emission (AE) is utilized as an inspection tool to identify the damage mechanisms regarding the 6.5%, 5.2%, and 4% decrease in tensile strength, strain at failure and modulus, respectively, in a comparative manner. The AE findings, remarking the weakening of the fiber-matrix interface after aging, are validated with scanning electron microscopy analysis. This study introduces an aging process-induced damage mechanism triggered with inhomogeneous water absorption for AFP manufactured CF/PEKK composites with in situ consolidation.
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    A Systematic Characterization Approach for Vacuum Bag Only Prepregs towards an Accurate Process Design
    (Mdpi, 2022) Arikan, Muhammed H.; Eroglu, Fatih; Eskizeybek, Volkan; Sukur, Emine Feyza; Yildiz, Mehmet; Sas, Hatice S.
    Aerospace-grade composite parts can be manufactured using Vacuum Bag Only prepregs through an accurate process design. Quality in the desired part can be realized by following process modeling, process optimization, and validation, which strongly depend on a primary and systematic material characterization methodology of the prepreg system and material constitutive behavior. The present study introduces a systematic characterization approach of a Vacuum Bag Only prepreg by covering the relevant material properties in an integrated manner with the process mechanisms of fluid flow, consolidation, and heat transfer. The characterization recipe is practiced under the categories of (i) resin system, (ii) fiber architecture, and (iii) thermal behavior. First, empirical models are successively developed for the cure-kinetics, glass transition temperature, and viscosity for the resin system. Then, the fiber architecture of the uncured prepreg system is identified with X-ray tomography to obtain the air permeability. Finally, the thermal characteristics of the prepreg and its constituents are experimentally characterized by adopting a novel specimen preparation technique for the specific heat capacity and thermal conductivity. Thus, this systematic approach is designed to provide the material data to process modeling with the motivation of a robust and integrated Vacuum Bag Only process design.
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    Effects of meso- and micro-scale defects on hygrothermal aging behavior of glass fiber reinforced composites
    (Wiley, 2022) Sukur, Emine Feyza; Elmas, Sinem; Seyyednourani, Mahsa; Eskizeybek, Volkan; Yildiz, Mehmet; Sas, Hatice S.
    Design and process-induced defects in fiber-reinforced polymers (FRPs) lead to fracture nucleation due to the stress concentrations. In addition to the degradation in mechanical properties, defects can accelerate aging of FRPs and limit their service life. Efforts to understand the impact of defects have largely focused on the mechanical performance of FRPs. However, their impact on aging performance has not yet been extensively investigated. Here, we report the effect of the meso-scale (missing yarn) and micro-scale (micro-crack) defects on the hygrothermal aging behavior of FRPs. Missing yarn defects were generated by pulling-out yarns in warp and weft directions of glass fabric. Then, micro-cracks were induced in composite laminates by acoustic emission controlled tensile loading/unloading. After exposing samples to the hygrothermal aging, we found that meso-scale defects deteriorate mechanical/thermomechanical performance, reaching 30% decrease in the flexural strength. Notably, even though increasing micro-crack density reduces the moisture saturation time, the aging time is reported as a more predominant design parameter, deteriorating the mechanical performance for micro-crack-induced FRPs.
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    Pseudo- retranslation: A novel perspective on translational intertextuality
    (Peter Lang Publishing Group, 2022) Yildiz, Mehmet
    Intertextuality is among the phenomena pivotal to the discussions on the originality/ authenticity of translated texts. Undoubtedly, translation proper is an intertextual production that is built on an antedating text, typically written in a foreign language. The author of the present paper observed a new case of textual interdependence - i.e., pseudoretranslation - where an academic author partially or completely uses another academic author's translation and presents it as a retranslation of a given source text. This paper avails of a corpus of 27 academic works (eleven master's theses, eight doctoral dissertations, five articles, two books and one conference paper), which were analysed to reveal the intertextual associations between them. These works from six different disciplines were purposively selected to include the Turkish (pseudo- re)translations of Milton Rokeach's five assumptions about the nature of human values in his seminal book The Nature of Human Values. Only the 27 works, purporting to have translated Rokeach's five assumptions from the original book, were included in the analyses. Intertextual similarity rates were operationalised as the primary parameter to reveal pseudo- retranslations and judge the degree of translational interdependence. R (Ver. 4.0.4), a statistical software program, was employed to generate the intertextual similarity rates and WCopyfind, a text comparison program, to produce the qualitative data. It was concluded from the results that the Turkish academic authors, particularly postgraduates, in the corpus chose to "pseudo- retranslate from" other Turkish academics' works rather than translate directly from the respective source text as they wrote in their native tongue. © Peter Lang GmbH Internationaler Verlag der Wissenschaften Berlin 2022. All rights reserved.
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    Reecriture feminine as a conceptual convergence: A paratext-driven analysis of Fitzgerald, Lattimore, Fagles, and Wilson's translations of The Odyssey
    (Logos Verlag Berling Gmbh, 2023) Yildiz, Mehmet; Altin, Merve
    Translation, as Andre Lefevere argues, is a form of rewriting, governed by various idiosyncratic and sociocultural factors and characterized by a certain level of ideological manipulation of the source text to conform to the norms and conventions of the target culture or fulfil ideological purposes. Resonating with this view, ecriture feminine (feminine writing or women's writing), as conceptualized by Helene Cixous, can be employed to make women more visible in literature and society by emancipating them from the dominant phallogocentric conceptualization through the invention of a new insurgent writing. By converging these two concepts, this paper (re)contextualizes reecriture feminine as a translational concept. It builds on the analyses of the English translations of Homer's Odyssey by Robert Fitzgerald (1961), Richmond Lattimore (1965), Robert Fagles (1996), and Emily Wilson (2017), the first woman to translate this classic into English, and of several paratexts on her translation and the previous ones.