Person: ÖZER, HAKKI
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ÖZER
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HAKKI
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Publication Sound insulation performance of honeycomb core aluminum sandwich panels with flexible epoxy-based foam infill(Elsevier Sci Ltd, 2023-05-11) Boztoprak, Yalçın; Ünal, Merve; Özada, Çağatay; Kuzu, Eslem; Özer, Hakkı; Ergin, Furkan; Yazıcı, Murat; Ünal, Merve; Özada, Çağatay; Kuzu, Eslem; ÖZER, HAKKI; Ergin, Furkan; YAZICI, MURAT; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0003-1714-7394; 0000-0003-1503-1232; 0000-0002-8720-7594; M-4741-2017; AAG-9987-2021; AAC-5342-2021; FFS-9528-2022; FOL-7608-2022; IVA-3471-2023The most distinctive features of sound insulation structures are their flexibility and porosity. Therefore, the flexible epoxy matrix material was made cellular using a suitable foaming agent. In addition, hollow glass mi-crospheres (HGMs) were added to the epoxy matrix. Thus, the sound wave refraction was increased by obtaining cavities in the cell walls. Structures with different densities and voids were created by changing the ratios of the filling material and foaming agents used in the sandwich. An aluminum (Al) honeycomb was used to protect the insulation materials' structural integrity and ensure the homogeneous distribution of sound waves. The effect of density differences on sound insulation values was investigated. The mechanical properties of sandwich struc-tures were determined using compression and three-point bending tests. The distribution of the filler in the matrix was visualized using SEM. TGA, DSC, thermal conductivity, dielectric, and flammability tests were also performed to determine their thermal, electrical, and flammability properties. During the formation of cells in the flexible epoxy, the HGMs were positioned in the cell wall by internal gas pressure. Low-density structures performed better at low frequencies, while high-density structures at high frequencies.Publication A sandwich panel that autonomously repairs sudden large holes and defects for tankers and pipelines carrying hazardous matter(Sage Publications Ltd, 2022-04-12) Özer, Hakkı; Kuzu, Eslem; Özada, Çağatay; Ünal, Merve; Kasım, Hasan; Yazıcı, Murat; ÖZER, HAKKI; Kuzu, Eslem; Özada, Çağatay; Ünal, Merve; YAZICI, MURAT; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0003-1503-1232; 0000-0002-8720-7594; AAC-5342-2021; M-4741-2017; AAG-9987-2021; FOL-7608-2022; FFS-9528-2022; AAG-9987-2021The self-healing of micro and macro cracks is vital for eliminating defects such as damage progression and loss of strength in structures. In this study, a polyurethane (PU) based geometrically self-healing sandwich structure was developed. The geometric healing agent, PU resin and activator, were filled into macrocapsules, and these capsules were filled into the Aluminum (Al) honeycomb cells. Self-healing of structural strength, large holes and cracks in developed sandwich structures were investigated by performing quasi-static compression and impact penetration tests. The sandwich structure with a self-healing capsules-filled core was damaged by subjecting it to quasi-static and penetration impact loads, and the healing agents in the broken capsules were mixed. The damage in the specimen was removed by geometric self-healing. Liquid and air permeability tests were applied to the PU foam used as a healing agent. No liquid permeability was observed in the structure. In addition, significant reductions in air permeability were obtained. Scanning electron microscope images were used to explore the characterization of the PU foam structure cells.Publication Development and characterization of self-healing microcapsules, and optimization of production parameters for microcapsule diameter and core content(Emerald Group Publishing Ltd, 2022-10-21) Özada, Çağatay; Ünal, Merve; Şahin, Eslem Kuzu; Özer, Hakkı; Motorcu, Ali Rıza; Yazıcı, Murat; Özada, Çağatay; Ünal, Merve; Şahin, Eslem Kuzu; ÖZER, HAKKI; YAZICI, MURAT; Fen Bilimleri Enstitüsü; Polimer Malzemeler Bölümü; 0000-0003-1503-1232; 0000-0002-8720-7594; M-4741-2017; AAG-9987-2021; AAC-5342-2021; GYE-4810-2022; FOL-7608-2022Purpose This study produced epoxy-filled urea-formaldehyde (UF) microcapsules (MCs) and T-403 amine MCs using the in situ technique. The Taguchi method was used to determine the effects of the control factors (temperature, stirring speed, core-shell ratio and surfactant concentration) affecting MCs' core diameter and core content and optimizing their optimum levels with a single criterion. Optimum control factor levels, which simultaneously provide maximum core diameter and core content of MCs, were determined by the PROMETHEE-GAIA multi-criteria optimization method. In addition, the optimized MC yield was analyzed by thermal camera images and compression test. Design/methodology/approach Microcracks in materials used for aerospace vehicles and automotive parts cause serious problems, so research on self-healing in materials science becomes critical. The damages caused by micro-cracks need to heal themselves quickly. The study has three aims: (1) production of self-healing MCs, mechanical and chemical characterization of produced MCs, (2) single-criteria and multi-criteria optimization of parameters providing maximum MC core diameter and core content, (3) investigation of self-healing property of produced MCs and evaluation. Firstly, MCs were produced to achieve these goals. Findings The optimized micro cures are buried in the epoxy matrix at different concentrations. Thermal camera images after damage indicate the presence of healing. An epoxy-amine MC consisting of a 10% by weight filled aluminum sandwich panel was prepared and subjected to a quasi-static compression test. It was determined that there is a strong bond between the UF shell and the epoxy resin. Originality/value The optimization of production factors has been realized to produce the most efficient MCs that heal using less expensive and more accessible methods.Publication Development of MNO2/PANI/SWCNT nanocomposite supercapacitor electrode and investigation of electrochemical performance(Bursa Uludağ Üniversitesi, 2023-09-25) Özada, Çağatay; Ünal, Merve; ÖZER, HAKKI; YAZICI, MURATIn this study, a manganese dioxide (MnO₂/polyaniline (PANI)/ single-walled carbon nanotube (SWCNT) nanocomposite electrode was prepared for pseudo-supercapacitors. To reduce the internal resistance of the electrode, increase the capacitance stability, and reduce the cost of single-walled carbon nanotubes, SWCNT was subjected to two-step acid etching. The purity of SWCNT was improved from ~95% to 99.98%. In addition, SWCNT was functionalized by this process. Thus, a nanocomposite was formed by coating PANI around SWCNT. MnO₂/PANI/SWCNT were synthesized using the hydrothermal method. Morphological, chemical and thermal analyses of the synthesized nanocomposite structure were carried out. In addition, X-ray diffraction (XRD) was used to determine the crystal structure. Electrochemical analyses were performed using a three-electrode system in a 1 M KOH electrolyte solution. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements were performed. The capacitance of the nanocomposite electrode at 400 cycles was314 mF/cm², and the capacitance retention stability was calculated at 73.24%. The results showed that the capacitance stability was high, and the supercapacitor was sensitive to redox reactions.