The present study aims to numerically examine two commonly used airfoils that provide high lift at low Reynolds numbers, using various turbulence models with the commercial code ANSYS Fluent 19. Eppler 423 airfoil is widely used in wind turbine blades, wings of gliders and R/C airplanes designed for sport flying and competitions thanks to high lift capability. NACA 6409 airfoil is seen in free-flight model planes. In literature review, it has been found that k-ω SST, k-kl-ω and 𝛾-𝑅𝑒𝜃 transition models have a good prediction in Cl-Cd estimation of drag bucket region, transition flow regime, and laminar separation point. In addition to RANS models, laminar model was also investigated. In order to ensure the accuracy and precision of numerical investigations; the grid sensitivity study and near wall model were used. The method of decomposition of flow direction vector procedure has been used to provide the advantage of simulating all angle of attacks using only a single mesh. The lift coefficient curves and polar diagrams were formed from the angle of attack of -4 degree up to the stall. Experimental data, XFoil analysis data and numerical analysis data were evaluated in terms of best glide ratio-(Cl/Cd)max and minimum sink-(Cl1.5/Cd)max criteria. As expected, at high angle of attack, the transition ramp on the upper surface moves forward and the pressure gradient became more adverse. The results showed that fine mesh gives better results than other mesh sizes and transitional γ-Reθ SST model was successful in modelling the transition event than other turbulence models.

In this study, NiO nanoparticle–reinforced PMMA nanocomposites were fabricated by melt blending, and the influence of extrusion mixing time on structural and thermal properties was examined. Mixing durations of 6 and 12 min were applied, and the materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). These analyses confirmed the presence of NiO within the PMMA matrix and indicated that prolonged mixing promoted particle agglomeration. Thermal behavior was assessed by thermogravimetric analysis (TGA) at heating rates of 5, 10, 15, and 20 K·min⁻¹, and activation energies of decomposition were calculated using the Kissinger, Takhor, and Augis–Bennett methods. The results showed that extended mixing reduced composite homogeneity and adversely affected thermal stability. Incorporation of NiO nanoparticles decreased both the onset decomposition temperature and the activation energy compared to pure PMMA, facilitating earlier degradation. At 620 K, pure PMMA exhibited ~8% mass loss, whereas the 12 min blend showed ~12% loss. These findings highlight the importance of nanoparticle dispersion and processing parameters in governing the degradation behavior of PMMA/NiO nanocomposites.

In order to take more stringent measures in fuel economy and achieve the determined performance targets, the automotive industry needs to reduce the weight of the vehicles it produces. For this reason, all automobile manufacturers have determined their own strategies. Some manufacturers use lighter aluminum, magnesium, and composite components in their cars. In this study, the joining techniques of lightweight materials such as welding and the processes of their industrial use have been examined. There is currently no single technology that can combine all metallic panels in a car body structure. However, it is known that various joining technologies are used together. With the potential to combine certain combinations of steel and aluminum, manufacturers and scientists continue to work to identify technologies with the highest potential for lightweight joining and put them into use in high-volume automobile production. Therefore, it is important to examine the weldability of light materials such as magnesium, titanium, and aluminum.

This study uses functionally graded material (FGM) consisting of aluminum (Al) and iron (Fe) produced by powder metallurgy method with different microstructures. Al and Fe powders are prepared, mixed at different ratios for each step, and compressed by the hot pressing method to obtain FGM. The four layer FGM composite was fabricated by employing powder metallurgy method. The layers were stacked with a surface of Al and Fe 80–20 wt% on top (1st layer) with succeeding layers of Al and Fe at (60–40 wt% (2nd layer), 40–60 wt% (3rd layer), and 20–80 wt% (4th layer)). The distributions at interfaces between the stages are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Obtained data indicate that Al and Fe are homogeneously distributed in the structure in all grades. Increasing the Fe ratio in the layers creates porosity in the Al phase. A Scherrer–Warren equation calculates grain sizes and the lattice parameters in XRD analyses. Vickers indentation is used to determine the hardness of the stages and interstages of the FGM. It is shown that the microstructural and mechanical properties of FGM composites increase by increasing Fe material composition. The results of 4th grade (20% Al + 80% Fe) composite showed improved interface layer microstructure and a maximum hardness of 105.75 HV for grades and 97 HV for interfaces of the FGM composite.

In this study, NiO nanoparticle–reinforced PMMA nanocomposites were fabricated by melt blending, and the influence of extrusion mixing time on structural and thermal properties was examined. Mixing durations of 6 and 12 minutes were applied, and the materials were characterized by X-ray diffraction (XRD) and scanning electron mi-croscopy (SEM). These analyses confirmed the presence of NiO within the PMMA ma-trix and indicated that prolonged mixing promoted particle agglomeration. Thermal behavior was assessed by thermogravimetric analysis (TGA) at heating rates of 5, 10, 15, and 20 °C·min⁻¹, and activation energies of decomposition were calculated using the Kissinger, Tachor, and Augis–Bennett methods. The results showed that extended mixing reduced composite homogeneity and adversely affected thermal stability. In-corporation of NiO nanoparticles decreased both the onset decomposition temperature and the activation energy compared to pure PMMA, facilitating earlier degradation. At 620 K, pure PMMA exhibited an 8% mass loss, whereas the 12-minute blend displayed a 12% loss. These findings highlight the importance of nanoparticle dispersion and processing parameters in governing the degradation behavior of PMMA/NiO nano-composites.

The thermal degradation behavior of polymer nanocomposites is strongly governed by nanoparticle dispersion; however, the relationship between dispersion homogeneity and degradation kinetics remains unclear. In this study, PMMA/NiFe₂O₄ nanocomposites were prepared using controlled melt mixing with different mixing times in order to systematically investigate the role of dispersion state on thermal degradation kinetics. Structural and morphological characterization was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM), while non-isothermal differential thermal analysis (DTA) was employed at multiple heating rates to evaluate degradation behavior.XRD results confirmed that the incorporation of NiFe₂O₄ nanoparticles did not alter the amorphous structure of the PMMA matrix. SEM analysis revealed that prolonged mixing significantly improved nanoparticle dispersion, whereas shorter mixing resulted in partial agglomeration. Despite comparable degradation peak temperatures for all samples, pronounced differences were observed in degradation kinetics. Activation energies calculated using Kissinger, Ozawa, and Augis–Bennett methods demonstrated that the PMMA-6 nanocomposite exhibited the highest activation energy (~270 kJ/mol), representing an increase of approximately 30% compared to neat PMMA and ~25% compared to the more homogeneously dispersed PMMA-12 sample.These results indicate that maximum nanoparticle dispersion does not necessarily correspond to maximum thermal resistance. Instead, an optimum dispersion state characterized by partial agglomeration and enhanced interfacial constraint governs the thermal degradation kinetics of PMMA/NiFe₂O₄ nanocomposites. This study highlights the critical role of processing-controlled dispersion in tailoring the thermal performance of polymer nanocomposites without inducing structural changes.