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Öğe Analysis of ply-wise failure of composite laminates with open holes(Walter De Gruyter Gmbh, 2022) Daricik, FatihFiber-reinforced composite materials may contain open holes according to the needs of service conditions. This research aims to determine the effect of the shape and size of the open-holes on the compressive strength of the carbon fiber/epoxy laminated composite material. The mechanical properties and the open-hole compressive failure of the laminate were introduced first. The experimental study was simulated with Finite element analysis and the difference between the experimental and numerical methods used to determine the compressive strength were compared. The results showed that the failure starts with matrix shear failure at the interface between the consecutive plies that have the greatest angle difference in fiber directions. The angle difference between the load and the reinforcement fibers is also important in determining the interface where the damage occurs. In terms of compressive strength, the shape and orientation of the holes are at least as important as the size of the holes.Öğe Carbon nanotube (CNT) modified carbon fiber/epoxy composite plates for the PEM fuel cell bipolar plate application(Pergamon-Elsevier Science Ltd, 2023) Daricik, Fatih; Topcu, Alparslan; Aydin, Kadir; Celik, SelahattinLight structures of the composite materials are prominent outcomes for reducing the total stack weight. However, the poor electrical properties of the composite structures pose an obstacle to wide employment as a bipolar plate for the PEMFC systems. In the current study, the carbon fiber/epoxy composite laminates were modified with the multi-walled carbon nanotube superconductor materials to overcome conductivity issues. The effects of CNTs additives in a range of 0.25-1.25% wt on the electrical, mechanical, and perfor-mance features of the carbon fiber/epoxy laminates were investigated. Electrical conduc-tivities of the nonconductive carbon fiber/epoxy plates increased with the rising additive ratio, as expected, and reached 120 S/cm for the 1.25% CNT reinforcement. Although the mechanical strength of the pristine composite BP is already satisfactory, CNTs can increase the flexural strength and flexural modulus of the BP up to 42% and 27%, respectively. Each composite plate was subjected to the single-cell performance test. 1.25% wt CNT modified plate was executed pretty close performance compared to the aluminum alloy (AA 3105) bipolar plate under the same conditions.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe Dynamic response optimization of a thermoplastic composite sandwich beam under random vibration(Taylor & Francis Inc, 2024) Oktav, Akin; Basaran, Murat Alper; Daricik, FatihThe dynamic response of a thermoplastic composite sandwich structure is optimized under random vibration. First, the experimental modal analysis data of a set of test samples are processed by a sequential set of statistical analysis such as descriptive statistics, factor analysis, and paired sample t-test. Then, the sample with the highest ability to represent the group is taken as the reference data. Three different computational models, which are defined according to whether the solid to be meshed is considered an area or a volume, are constructed. Modal analysis results of the computational models are compared to the reference experimental data to evaluate the performance of the models. To predict the dynamic response of the sandwich beam, it is excited through a random signal in the transverse direction. The nodal acceleration responses are computed in 17 evenly spaced points located on the upper finishing layer of the sandwich beam. Finally, a geometry optimization study is conducted to predict the optimum thicknesses of the 7 layers bonded together to form the sandwich beam. The optimum layer thicknesses that minimize the nodal accelerations at 17 evenly spaced points on the sandwich beam are computed. The current study shows that the shell model has the closest values to the experimental data compared to other models. As far as the dynamic response of a TPC sandwich structure is concerned, it is concluded that the shell model better represents the structure during the modeling phase and leads to concurrently reduced weight and nodal acceleration, when optimized.Öğe Effects of carbon nanotube size on the mode I interlaminar fracture behavior of E-glass/epoxy nanocomposites: Static loading(Wiley, 2022) Daricik, Fatih; Aslan, ZuleyhaThree types of carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs) were used to manufacture MWCNT-modified laminates. The effects of the MWCNTs on the mode I interlaminar fracture toughness and the fracture propagation were investigated experimentally. Fractured surfaces were inspected with SEM micrographs to justify the effects of MWCNTs on the mode I fracture of the laminate. The short-thin MWCNTs in a weight ratio of 0.3% increases mode I interlaminar fracture resistance of the laminate by about 2 times. The effects of long-thin and long-thick MWCNTs are quite low. Polymer crazing is the most important mechanism to improve interlaminar fracture properties.Öğe Effects of Short-Term Thermal Aging on the Fracture Behavior of 3D-Printed Polymers(Springer, 2021) Daricik, Fatih; Delibas, Hulusi; Canbolat, Gokhan; Topcu, Alparslan3D printing technologies offer numerous advantages and have attracted the attention of researchers recently. Yet, the most commonly preferred additive manufacturing system is the extrusion-based process that is called fused deposition modeling (FDM) as it is simple, low cost, and prone to customization. In this paper, the effects of the short-term aging of the additively manufactured PLA and ABS specimens were investigated experimentally. The test specimens were aged by keeping them at ambient temperatures of - 80, - 20, 60, 100 degrees C for 10, 20, and 30 days. Thermally aged specimens and the pristine specimens were forced to fracture with bending load at room temperature. Thus, the permanent effects of thermal aging of the specimens were investigated utilizing the load-deflection curve, plane-strain fracture toughness, and the morphologies of fracture surfaces. It was concluded that the printed PLA materials are more susceptible to the thermal aging than the ABS printed materials. The contraction and expansion of the fused polymer filaments affect directly the bonding strength between the adjacent layers. Therefore, plane-strain fracture characteristics of the FDM polymer materials exposed to thermal aging differ according to the filament orientation and the aging time.Öğe Experimental investigations on metallization in the surface modified additively manufactured plastic substrates using DC sputtering(Sage Publications Ltd, 2024) Aktitiz, Ismail; Daricik, Fatih; Aydin, Alkim; Aydin, KadirThe application of copper surface coating to plastic structures offers numerous advantages, including high thermal and electrical conductivity, improved mechanical properties, good corrosion resistance, decorative applications, and enhancements in working temperatures. Besides these advantages, producing plastic structures with 3D printing and applying surface coating enables the final structures to become functional plastic structures adaptable to different fields. In this study, 3D plastic structures were produced using the fused deposition modeling method. Pristine, dichloromethane dipping, dichloromethane vapor, cold oxygen plasma, and mechanical abrasion surface treatments were applied to determine the optimal surface treatment between copper and the plastic substrate before copper coating. Subsequently, copper coating on plastic structures was completed using the DC sputtering technique. The surface topography, optical, electrical, and structural properties of the produced plastic structures were examined. According to X-ray diffraction analysis results, the (111), (200), (220), and (311) crystal planes confirm the presence of copper. The electrical conductivity values of the plastic structures reached 7.87 x 105 S/m. Contact angle measurement results indicate that the applied surface treatments increased the contact angles to 88.309 degrees, leading the coated plastic structures to exhibit a more hydrophobic behavior.Öğe Failure of surface modification 3D printed polymer materials by UV/ozone irradiation(Pergamon-Elsevier Science Ltd, 2023) Korkut, Volkan; Daricik, Fatih; Aktitiz, Ismail; Aydin, KadirIn today's technology, AM processes are widely adopted in the aerospace, energy, automotive, medicine, and agriculture industries. Fused Deposition Modeling (FDM) is one of the most remarkable methods in the AM family because of its superiorities. Besides the advantages pro-vided, the mechanical strength of the printed parts is still not at a satisfactory level. Here, there are various secondary processes applied to polymer materials to improve both the mechanical properties and functionality of the printed part. Among these processes, the UV/O3 surface treatment method stands out as the most suitable one in terms of ease of application. In this study, two different infill orientation angles were applied to two standard test models. The fabrication process was initiated using suitable process parameters for filaments made of Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) materials. The purpose of this investigation was to examine the mechanical strength of 3D printed polymer structures. For the same purpose, the UV/O3 (UV/Ozone) process was applied to the manufactured samples. The samples are then subjected to tensile and compression tests, Shore surface hardness measurements and Scanning Electron Microscopy (SEM) analyze for both the evaluation of mechanical properties and the examination of fracture surface structures. Consequently, significant increases of 28.33%, 25.21%, 27.90%, and 32.92% were observed in material surface hardness levels. This study is important in terms of presenting that the mechanical properties of 3D printed parts can be significantly improved with UV/O3 application, which is an effective and a practical process.Öğe Investigation of a fiber reinforced polymer composite tube by two way coupling fluid-structure interaction(Techno-Press, 2022) Daricik, Fatih; Canbolat, Gokhan; Koru, MuratFluid-Structure Interaction (FSI) modeling is highly effective to reveal deformations, fatigue failures, and stresses on a solid domain caused by the fluid flow. Mechanical properties of the solid structures and the thermophysical properties of fluids can change under different operating conditions. In this study, we investigated the interaction of [45/-45]2 wounded composite tubes with the fluid flows suddenly pressurized to 5 Bar, 10 Bar, and 15 Bar at the ambient temperatures of 24 degrees C, 66 degrees C, and 82 degrees C, respectively. Numerical analyzes were performed under each temperature and pressure condition and the results were compared depending on the time in a period and along the length of the tube. The main purpose of this study is to present the effects of the variations in fluid characteristics by temperature and pressure on the structural response. The variation of the thermophysical properties of the fluid directly affects the deformation and stress in the material due to the Wall Shear Stress (WSS) generated by the fluid flow. The increase or decrease in WSS directly affected the deformations. Results show that the increase in deformation is more than 50% between 5 Bar and 10 Bar for the same operating condition and it is more than 100% between 5 Bar and 15 Bar by the increase in pressure, as expected in terms of the solid mechanics. In the case of the increase in the temperature of fluid and ambient, the WSS and Von Mises stress decrease while the slight increases of deformations take place on the tube. On the other hand, two-way FSI modeling is needed to observe the effects of hydraulic shock and developing flow on the structural response of composite tubes.Öğe Investigation of Rupture Risk of Thoracic Aortic Aneurysms via Fluid-Structure Interaction and Artificial Intelligence Method(Springer Heidelberg, 2024) Koru, Murat; Canbolat, Gokhan; Daricik, Fatih; Karahan, Oguz; Etli, Mustafa; Korkmaz, ErgunPatient-specific studies on vascular flows have significantly increased for hemodynamics due to the need for different observation techniques in clinical practice. In this study, we investigate aortic aneurysms in terms of deformation, stress, and rupture risk. The effect of Ascending Aortic Diameter (AAD) was investigated in different aortic arches (19.81 mm, 42.94 mm, and 48.01 mm) via Computational Fluid Dynamics (CFD), Two-way coupling Fluid-Structure Interactions (FSI) and deep learning. The non-newtonian Carreau viscosity model was utilized with patient-specific velocity waveform. Deformations, Wall Shear Stresses (WSSs), von Mises stress, and rupture risk were presented by safety factors. Results show that the WSS distribution is distinctly higher in rigid cases than the elastic cases. Although WSS values rise with the increase in AAD, aneurysm regions indicate low WSS values in both rigid and elastic artery solutions. For the given AADs, the deformations are 2.75 mm, 6. 82 mm, and 8.48 mm and Equivalent von Mises stresses are 0.16 MPa, 0.46 MPa, and 0.53 MPa. When the rupture risk was evaluated for the arteries, the results showed that the aneurysm with AAD of 48.01 mm poses a risk up to three times more than AAD of 19.81 mm. In addition, an Artificial neural network (ANN) method was developed to predict the rupture risk with a 98.6% accurate prediction by numerical data. As a result, FSI could indicate more accurately the level of rupture risk than the rigid artery assumptions to guide the clinical assessments and deep learning methods could decrease the computational costs according to CFD and FSI.Öğe Metallization of 3D Printed Polylactic Acid Polymer Structures via Radio-Frequency Sputtering(Springer, 2025) Aktitiz, Ismail; Daricik, Fatih; Aydin, Alkim; Aydin, KadirThe metallization of polymer structures eliminates disadvantages such as low electrical conductivity, undesirable mechanical properties, degradation under different environmental conditions such as UV radiation and humidity, and poor thermal properties, thereby enabling the achievement of more functional polymer structures. 3D printing provides production flexibility by allowing the manufacture of polymer, ceramic, metal, and composite materials with any level of complexity and intricacy. This study aims to investigate the improvement of the drawbacks associated with polymers, by combining the advantages of polymers and metals through 3D printing and surface modification. The newly acquired features will offer researchers and users significant freedom in various applications. Polylactic acid was used to additively manufacture the polymer structures by using fused deposition modeling. Subsequently, the surfaces of polymer structures were subjected to surface treatment methods: as-printed, dichloromethane dipping, dichloromethane vapor, cold oxygen plasma, and sandpaper. The metallization process was completed using the RF sputtering technique with aluminum as the target material. To examine the morphological, structural, optical, and electrical properties of the metalized structures, various analyses were conducted, including scanning electron microscopy, energy-dispersive spectroscopy analysis, atomic force microscopy, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analysis, ultraviolet-visible-near-infrared (UV-VIS-NIR) analysis, contact angle measurement, ellipsometry analysis, and electrical resistance measurement. The results showed improvements in surface roughness due to the applied surface treatments. EDX and XRD analyses confirmed the presence of aluminum in the polymer structure. Electrical conductivity values of 0.32 x 106 S m-1 were achieved at a thickness of 1000 nm. Contact angles increased up to 91.728 degrees.Öğe Mode-II Fracture and Residual Flexural Strength of MWCNT Modified E-Glass/Epoxy Laminates(Wiley, 2025) Yildiz, Coskun; Daricik, FatihIn this study, three types of carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs) were used to modify the mode-II interlaminar fracture characteristics and residual bending resistance of E-glass/epoxy composite laminates. The MWCNTs with different weight ratios were added into the matrix material, and the mode-II interlaminar fracture toughness and the fracture propagation were investigated in accordance with the relevant ASTM standards. Fractured surfaces were inspected with SEM micrographs to justify the effects of MWCNTs on the mode-II fracture of the laminate. The MWCNTs increased the adhesion of constituents in the laminates and obstructed the propagation of delamination. The MWCNTs enhanced mode-II interlaminar fracture toughness and bending stiffness of the E-glass/epoxy laminates. The short-thin MWCNTs at 0.3 wt% increased mode-II interlaminar fracture resistance of the laminate by about 2 times. The effects of long-thin and long-thick MWCNTs are quite low.
