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Publication Metadata only A facile method for cross-linking of methacrylated wood fibers for engineered wood composites(Elsevier B.V., 2023) Bengü, Başak; Biçer, Aziz; Yarıcı, Tugay; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Sarıoğlu, Ebru; Turhan, Emine Ayşe; Karaz, Selcan; Erkey, Can; Şenses, Erkan; PhD Student; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM), Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; 29633; 280298Chemical modifications are widely used to enhance the properties of wood composites and create a strong bonding mechanism for enhancing the dimensional stability, water resistance as well as decreasing carcinogenic formaldehyde emission. Esterification is the most-known modification way to enhance the durability of wood composites, but it does not improve mechanical performance. In this work, we demonstrated a two-step, easy and quick wood surface modification strategy based on microwave heating and UV crosslinking. Firstly, the fiber surface was reacted with methacrylic anhydride, then using methacrylated groups on wood, the fibers are covalently linked. As a proof-of-concept the fibers cross-linked within five minutes under UV radiation using benzophenone solution. Then, the effect of crosslinked wood fiber on the properties of mechanical and swelling of fiberboard were studied. Using SEM, FTIR-ATR, and swelling tests, we investigated the wood-based products' reaction mechanism, morphology, and internal bonding strength. The chemical cross-linking gives stronger bonding, compared to hydrogen bonding, between fibers even in wet conditions, resulting in a cross-linked foam-like structure. Also, wood panels were fabricated, compared to unmodified fibers, the internal bond strength and dimensional stability of fiberboards increased slightly. Overall, these results show that chemical cross-linking of wood fibers can be a fast and promising way to produce multi-functional wood composites.Publication Metadata only A grid of dielectric sensors to monitor mold filling and resin cure in resin transfer molding(Elsevier Sci Ltd, 2009) N/A; Department of Mechanical Engineering; Yenilmez, Bekir; Sözer, Murat; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 10357A grid of 50 dielectric sensors has been embedded in the walls of a mold to monitor resin transfer molding (RTM). The capacitance of each sensor increased as resin occupied the space between sensor plates, and it decreased with curing. Monitoring data can be used for process control to prevent dry spots and to determine when to de-mold the part. In previous studies, Skordos et al. [Skordos AA, Karkanas PI, Partridge IK. A dielectric sensor for measuring flow in resin transfer molding. Meas Sci Technol 2000; 11:25-31] used a lineal sensor, Hegg et al. [Hegg MC, Ogale A, Mescher A, Mamishev AV, Minaie B. Remote monitoring of resin transfer molding processes by distributed dielectric sensors. J Compos Mater 2005;39(17)] used three large sensors. As experimentally shown in this study, these lineal or large-plate dielectric sensors may mislead since a sensor measures total fraction of the sensor's plate area occupied by resin but not the resin's whereabouts. To avoid ambiguity and yet maintain detailed monitoring, a sensor grid was made at the projections of embedded orthogonal electrodes. The developed sensor operation system eliminated tedious and costly manufacturing of conventionally shielded separate sensors. The success of the developed sensor system was demonstrated in RTM experiments.Publication Metadata only A novel mold design for one-continuous permeability measurement of fiber preforms(Sage Publications Ltd, 2015) N/A; N/A; Department of Mechanical Engineering; Yalçınkaya, Mehmet Akif; Sarıoğlu, Ayşen; Sözer, Murat; PhD Student; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 110357One-continuous permeability measurement experiments allow measuring permeability of a fiber preform within a range of fiber volume fractions by conducting a single unsaturated (a.k.a. transient) flow experiment on a dry specimen at an initial thickness, and a set of saturated flow experiments on the wetted specimen by varying the thickness of the mold cavity. This approach allows quicker database construction and reduces the effect of inherent variation of fabric structure caused by inconsistent labor on permeability. In this study, the drawbacks of previous mold designs are eliminated by using appropriate sealing, gap thickness adjustment mechanism and features that allow straightforward and reliable manual operation. Experiments for three different fabric types are conducted and the results are discussed. It is mainly observed that the unsaturated permeability is higher than the saturated permeability.Publication Restricted Assessing potential of [BMIM][MeSO4] in ionic liquid/metal organic framework composites for CO2 separation(Koç University, 2019) Kulak, Harun; Keskin, Seda; 0000-0001-5968-0336; Koç University Graduate School of Sciences and Engineering; Chemical and Biological Engineering; 40548Publication Restricted Combining molecular simulations and machine learning to unlock gas separation performances of MOFs and MOF-based composites(Koç University, 2024) Harman, Hilal Dağlar; Keskin, Seda; 0000-0001-5968-0336; Koç University Graduate School of Sciences and Engineering; Chemical and Biological Engineering; 40548Publication Metadata only Compaction of e-glass fabric preforms in the vacuum infusion process, A: characterization experiments(Elsevier Sci Ltd, 2009) N/A; Department of Mechanical Engineering; Yenilmez, Bekir; Sözer, Murat; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 110357An experimental procedure was designed to realistically characterize the compaction behavior of e-glass fabric preforms during initial application of vacuum and mold filling stages of Vacuum Infusion (VI). To mimic VI, the loading (compaction) was done on a dry preform, and the unloading (decompaction) was done after the preform was saturated with resin. When fabrics were wetted at constant full compaction pressure, a significant decrease in thickness was observed for the random fabric, but not for woven and biaxial fabrics. The rate of change of thickness, ∂h/∂t had different signs and order of magnitudes when various constant compaction pressures were applied during fiber relaxation stage. Thus, previous compaction-mold filling models based on static relationship between thickness and compaction pressure do not appropriately simulate the compaction physics of VI. Time-dependent database of this study is a useful and straightforward tool to model VI, as demonstrated in Part B of this study.Publication Metadata only Compaction of e-glass fabric preforms in the vacuum infusion process: (a) use of characterization database in a model and (b) experiments(Sage Publications Ltd, 2013) N/A; Department of Mechanical Engineering; Yenilmez, Bekir; Sözer, Murat; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 110357Compaction of e-glass fabric preforms (random, woven and biaxial) embedded with a distribution medium (polypropylene) is coupled with 1D resin (polyester) flow during initial application of vacuum, mold filling and fiber relaxation stages of vacuum infusion. In our previous study,(1) the compaction characterization procedure had been designed and conducted to realistically model the compaction behavior of fiber preforms in vacuum infusion such that the loading was done on a dry specimen; fiber settling was allowed under constant compaction pressure; unloading was done after the specimen was wetted and the fiber relaxation was characterized at constant pressure. To investigate the effects of characterization components on the part thickness evolution, two compaction models (unloading only and unloading and time-dependent relaxation) were coupled with two models of flow (uncoupled and coupled pressure-thickness-permeability). The results of the coupled model of unloading and time-dependent relaxation and coupled pressure-thickness-permeability was the closest to the vacuum infusion experiments.Publication Metadata only Constraints on monitoring resin flow in the resin transfer molding (RTM) process by using thermocouple sensors(Elsevier Sci Ltd, 2007) N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Tunçol, Göker; Danışman, Murat; Kaynar, Alper; Sözer, Murat; Master Student; Master Student; Undergraduate Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; 110357In this study, a thermocouple sensor system was used to monitor the resin transfer molding (RTM) process. These sensors are low-cost and durable; and they do not disturb the resin flow. They can be used if the inlet resin is either hotter or colder than the mold walls. In experiments of this study, much of the hot resin’s internal energy was transferred to cold mold walls by conduction, when the mold parts were made of a material with high thermal conductivity, such as aluminum. A mathematical model based on 1D flow and 2D unsteady energy conservation was developed to investigate the heat transfer between resin and mold walls. The numerical solution of this model is in qualitative agreement with the results of our experiments. The thermocouple sensor system developed is more useful with the following process parameters: low thermal conductivity of mold material, high resin flow rate, high temperature difference between inlet resin and initial mold walls, and high specific heat of resin. However, for the typical use of RTM materials and typical injection parameters, thermocouples should not be preferred over other sensor types and should be used with caution due to the shortcomings investigated in this study.Publication Restricted Design of a functional composite membrane via particle stabilized emulsion templating(Koç University, 2012) Kanyas, Selin; Kızılel, Seda; 0000-0001-9092-2698; Koç University Graduate School of Sciences and Engineering; Materials Science and Engineering; 28376Publication Metadata only Design of curved composite panels for optimal dynamic response using lamination parameters(Elsevier Sci Ltd, 2018) N/A; Department of Mechanical Engineering; Serhat, Gökhan; Başdoğan, İpek; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179940In this paper, dynamic response of composite panels is investigated using lamination parameters as design variables. Finite element analyses are performed to observe the individual and combined effects of different panel aspect ratios, curvatures and boundary conditions on the dynamic responses. Fundamental frequency contours for curved panels are obtained in lamination parameters domain and optimal points yielding maximum values are found. Subsequently, forced dynamic analyses are carried out to calculate equivalent radiated power (ERP) for the panels under harmonic pressure excitation. ERP contours at the maximum fundamental frequency are presented. Optimal lamination parameters providing minimum ERP are determined for different excitation frequencies and their effective frequency bands are shown. The relationship between the designs optimized for maximum fundamental frequency and minimum ERP responses is investigated to study the effectiveness of the frequency maximization technique. The results demonstrate the potential of using lamination parameters technique in the design of curved composite panels for optimal dynamic response and provide valuable insight on the effect of various design parameters.