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    Comparison of notch fabrication methods on the impact strength of FDM-3D-printed PLA specimens
    (Walter De Gruyter Gmbh, 2023) Eryildiz, Meltem
    In this study, the effect of the notch fabrication method (printing the notch on the part, and machining the notch) on the impact results of 3D-printed polylactic acid (PLA) was investigated. Sensitivity to build orientation was also noted in both test situations. The impact test specimens were printed using an FDM-based printer with or without a notch at various build and print orientations. Un-notched specimens were then machined to create notches. To simulate the impact effects, Ansys software was employed to create a finite element model, and the results of the finite element analysis were consistent with the experimental results. According to the findings, the impact strength of the specimens with 3D-printed notches increased by 11-38% compared to specimens whose notch was machined after the rectangular bars were 3D printed. In addition, it has been observed that the build and print orientations affect the impact strength.
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    Determination of the Effective Fused Deposition Modeling Process Parameters on the Mechanical Properties of Carbon Fiber-Reinforced Polypropylene Parts
    (Amer Soc Testing Materials, 2024) Eryildiz, Meltem; Kosa, Ergin; Yavuzer, Bekir; Akgun, Ismail Cem
    Additive manufacturing is gaining popularity for producing components in industries such as automotive, aerospace, and medicine due to its potential to minimize material waste. Because the strength of the 3-D-printed part is so important, it's crucial to do research and optimize process parameters to make the printed parts as strong as possible. This work focuses on the experimental investigation and discussion of the tensile and impact strength of parts made from carbon fiber-reinforced polypropylene (PP-CF) using the fused deposition modeling (FDM) technique. Various process parameters, including infill pattern, infill density, layer thickness, and build orientation, are examined on three different levels to determine their influence on the tensile and impact strength of the printed part. The outcomes of the analysis of variance (ANOVA) analysis reveal that infill density primarily affects impact strength, whereas layer thickness significantly influences tensile strength. The optimal combination of parameters leading to the maximum tensile and impact strength consists of a grid infill pattern, 60 % infill density, 0.36-mm layer thickness, and a 45 degrees build orientation. Furthermore, fracture surface analysis is consistent with mechanical test results.
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    Experimental investigation and simulation of 3D printed sandwich structures with novel core topologies under bending loads
    (Walter De Gruyter Gmbh, 2023) Eryildiz, Meltem
    In a range of applications, such as the automotive, aerospace, and shipbuilding sectors, where weight reduction is essential, sandwich structures are getting more popular. The performance of sandwich structures in bending can be enhanced by using lightweight core topologies. In this study, six different novel and new core topologies were designed with CATIA V5. Polylactic acid (PLA) sandwich structures with new core designs were produced using the fused deposition modeling (FDM) additive manufacturing method. In order to determine the mechanical characteristics of these six designed core topologies, three-point bending tests on sandwich structures were performed. The influence of core topology on the flexural characteristics of lightweight sandwich structures was investigated to appropriately choose and design the core topology of the sandwich structures to meet desired structural requirements. To evaluate the flexural behavior of sandwich structures, finite element simulation using ANSYS Workbench 2021 R2 was also performed. Both the experimental data and simulation were in good agreement and clearly showed that the sandwich structure with the triple bow core exhibited the highest mechanical properties. These results provide new perspectives on the investigation of the mechanical response of sandwich structures, which can be beneficial for many other industries and applications.
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    Fabrication of Drug-Loaded 3D-Printed Bone Scaffolds with Radial Gradient Porosity
    (Springer, 2023) Eryildiz, Meltem
    As a result of the combination of better mechanical and biological properties, gradient porous scaffolds are becoming more and more interesting alternatives for bioengineering and medical implants. In this study, drug-loaded functionally radial gradient scaffolds were investigated. Drug-loaded polylactic acid scaffolds with radial gradient porosities with different infill zones that mimic the heterogeneous bone structure were designed and manufactured. The PLA scaffolds with radial gradients were produced using the fused deposition modeling (FDM) method with gyroid infill Homogeneous porosity scaffolds were also tested to compare the results. The porosity, cell proliferation, drug release, and compressive strength of the fabricated 3D printed scaffolds were all tested in vitro. According to findings, the scaffolds with radial gradients contained the highest cell proliferation and drug release results but exhibited decreased mechanical strength because of the increased porosity. The drug-loaded radial gradient scaffolds fabricated in this work could be used as bone scaffolds to supply antibiotics, and they have compressive strength and cell proliferation levels that are comparable to real bones. [GRAPHICS] .
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    Influence of Process Parameters on the Shape Recovery Properties of 4D-Printed Polylactic Acid Parts Produced by Fused Deposition Modeling
    (Springer, 2023) Eryildiz, Meltem
    Four-dimensional (4D) printing technology allows printed parts to further alter their shapes or functions in response to external stimulus. 4D printing has been suggested for several potential applications in a range of industries, such as smart actuators, soft robotics, biomedical, and electronics. Shape memory polymers (SMP), which have the ability to change shape when heated, are programmable and deformable materials that are particularly well-suited for 4D printing. This study investigated the effect of 4D printing process parameters on the percentage of shape recovery. The selection of the appropriate process parameters is crucial to the success of 4D printing. Despite the large number of studies on the use of SMP, there is currently insufficient information on the relationship between the process parameters of the 4D printing process. The shape memory effect of the samples was examined by adjusting the sample thickness, nozzle temperature, deformation temperature, and holding time to achieve maximum percentage recovery for polylactic acid (PLA) using Taguchi's L16 orthogonal array. ANOVA was used to examine the impact of the process parameters taken into consideration. The results of the experiment showed that the sample thickness had the greatest influence. According to the results, the shape recovery percentage of the printed structures was enhanced by increasing the deformation temperature, holding temperature, and nozzle temperature while increasing the total thickness of the sample had a negative impact on shape recovery. A regression model on the recovery percentage against the process parameters is developed. This study has the feature of being a reference for future 4D printing studies.
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    Scaffold fabrication from drug loaded HNT reinforced polylactic acid by FDM for biomedical applications
    (Wiley, 2023) Kokcu, Ilknur; Eryildiz, Meltem; Altan, Mirigul; Ertugrul, Melek Ipek; Odabas, Sedat
    In this study, multifunctional polymer nanocomposite scaffolds were fabricated by the fused deposition method (FDM) for biomedical applications. First, halloysite nanotube reinforced (1-5 wt%) polylactic acid filaments were prepared by melt mixing process. For the selected compositions, HNT was loaded with metformin (MET) by electrostatic interactions. The characterization of the scaffolds was observed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The morphology of the nanocomposite scaffolds was investigated by scanning electron microscope. Mechanical behavior of the scaffolds was determined by tensile, compression, and three-point flexural tests. It has been seen that 3%wt of HNT loading showed 124%, 145%, and 41% increments in tensile, compression, and three-point flexural strength of the scaffolds, respectively. In-vitro drug release and cell viability of the scaffolds were also examined. According to the cell viability result, a better cell proliferation regimen was achieved in all HNT-containing groups without any cytotoxicity effect. Also, approximately 50% of the total drug was released from the scaffolds at the end of 120 h. Finally, it has been seen that the developed scaffolds show promise for bone regeneration and replacement of bone.