WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394

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Start date: 2025Publisher: search.filters.publisher.Sage Publications Ltd

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Now showing 1 - 6 of 6
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Evaluating the Effects of Design and Manufacturing Parameters on Friction at the Surrogate Skin-3D Textile Interface
    (Sage Publications Ltd, 2025-10-30) Temel-Cicek, Mevra; Cicek, Umur I.; Lloyd, Alex B.; Johnson, Andrew A.
    Additive manufacturing (AM) is increasingly employed in the development of 3D-printed wearables, including medical wrist supports, textiles, and protective garments. While the general tribological behavior of 3D-printed components has been widely studied, limited research has focused on the friction behavior of 3D-printed wearables when in contact with human skin, which is a crucial factor for improving wearer comfort by minimizing local skin friction. This study, therefore, investigates the influence of material type, manufacturing technology, and print parameters of 3D-printed textiles on frictional behavior against skin. Specimens were fabricated using three AM technologies: material extrusion (MEX), vat photopolymerization (VATP), and powder bed fusion (PBF). Each technology employed various materials and print parameters, specifically layer thickness (ranging from 0.05 to 0.3 mm) and print orientations (horizontal and vertical). Friction was measured using a custom-built handheld device at the interface between 3D-printed specimens and two surrogate skin models: lorica (representing the dorsal forearm) and silicone (representing the chest). The results revealed that friction was significantly influenced by both layer thickness and print orientation. For MEX specimens, acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, and polycarbonate showed the highest friction, while for VATP, durable resin resulted in the highest friction coefficient. In contrast, PBF specimens exhibited very similar frictional behavior. Regarding layer thickness, higher values consistently resulted in the highest friction coefficients, regardless of manufacturing method or material type. These findings provide valuable insights for designers and engineers seeking to optimize the comfort of 3D-printed wearables, guiding the selection of suitable AM processes and parameters for products intended for direct skin contact.
  • Article
    Failure Analysis of Fused Deposition Modeling 3D Printed Poly Lactic Acid Polymer
    (Sage Publications Ltd, 2025-10-04) Yilmaz, Cagatay; Eltahir, Sara Saeed Abdulrahman
    Additive manufacturing, commonly known as 3D printing (AM), has emerged as one of the most transformative technological advances in the last few decades in global manufacturing, as it allows for the production of intricate components without the use of costly molds. Fused Deposition Modeling (FDM) is widely adopted among various AM techniques due to its accessibility and effectiveness. FDM 3D-printed PLA (Poly Lactic Acid) shows a transversely isotopic symmetry similar to laminated composite structures. Therefore, classical lamination theory can be applied to FDM 3D-printed PLA. This study attempts to expand the knowledge by relying on classical lamination theory and several imposed failure theories like maximum stress, Tsai-Hill, Tsai-Wu, and Hashin to determine how FDM 3D printing of PLA fails. We investigate eight different raster orientations (0 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees) and compare the theoretical prediction of strength with experimental findings. With this comprehensive analysis, we are seeking to better understand the failure analysis of FDM 3D printed PLA. The maximum stress, Tsai-Wu, Tsai-Hill, and Hashin failure theories show good agreement with experimental findings for 0 degrees and 90 degrees raster orientations. As the raster orientation shifts from 0 degrees, the discrepancy between experimental results and theoretical predictions increases, peaks at mid-angles, and then decreases, becoming negligible at 90 degrees.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Effect of Multi-Cell Approach on Crashworthiness Performance of 3D-Printed Thin-Walled Structures Under Lateral Compression Loading for Unmanned Aerial Vehicle Applications
    (Sage Publications Ltd, 2025-06-02) Atahan, M. Gokhan; Zeybek, Halil; Gokhan Atahan, M.
    Recent technological advancements in unmanned aerial vehicles have led to their use in various military and civilian applications. However, weather conditions, operator faults, and electronic or mechanical problems can result in unmanned aerial vehicle accidents. In the event of an accident, energy-absorbing structures can be placed in specific regions of vehicles to protect sensitive and costly cameras, sensors, and cargo from damage, while also preserving the vehicle's structural integrity. In this study, thin-walled energy absorbers with circular, square, hexagonal, and reentrant geometries were proposed, and the experimental investigation focused on the effect of increasing the number of cells on their crashworthiness performance and deformation mechanisms. Lateral compressive load was applied to thin-walled structures produced by fused deposition modeling technology using advanced polylactic acid filament. Experimental results showed that the triple-cell reentrant thin-walled structure demonstrated promising results for unmanned aerial vehicle applications, as it exhibited the highest mean crushing force, energy absorption, and specific energy absorption values. Thanks to the unique geometry of the reentrant structure, a gradual collapse mode was observed, and as a result, the triple-cell reentrant structure exhibited high energy absorption performance.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Compression Performance of 3D-Printed Ant-Inspired Lattice Structures: An Innovative Design Approach
    (Sage Publications Ltd, 2025-01-12) Atahan, Mithat Gokhan; Saglam, Selman
    In this study, three different ant-inspired lattice design types: single, double, and inverted double structures were considered due to ants' excellent load-carrying weight ratio. Lattice structures were fabricated using the 3D printing method and polylactic acid filament was used as a printing material. The true blueprint images of the ant were used to obtain the parametric dimensions of the ant-inspired lattice structure. Hence, the presented innovative method for designing lattice structures can be a promising option for industrial sectors requiring high-strength structures. The quasi-static axial compression tests were conducted to evaluate the compression performance of the novel lattice structures. The compression performance of ant-inspired single lattice structures was compared based on specific force, specific energy absorption, and specific stiffness at different height values. The deformation stages and damage regions of ant-inspired lattice structures were analyzed to identify their critical regions during compression tests. The results indicated that as the height value increased, there was a notable decrease in specific force, specific energy absorption, and specific stiffness, along with buckling damage in the ant-inspired single lattice structures. Among the three design types, the ant-inspired inverted double lattice structure showed better compression performance compared to the ant-inspired double lattice structure; however, the ant-inspired single lattice structure with a height of 30 mm exhibited the highest overall compression performance.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 4
    Comparative Study on Bending Performances of 3D-Printed Monolithic and Adhesively Bonded Sandwich Structures With Various Auxetic Cores: An Innovative Production Approach
    (Sage Publications Ltd, 2025-03-28) Atahan, Mithat Gokhan; Sevim, Caglar; Demirbas, Munise Didem; Apalak, Mustafa Kemal
    The cores of sandwich structures are typically produced monolithically using lightweight materials and specific geometries. In recent years, the advancements in additive manufacturing have enabled the design and production of novel sandwich core configurations with auxetic behavior and high energy absorption capability. In this study, an innovative production approach, namely adhesively bonded sandwich structures with auxetic cores, was proposed to ensure significant manufacturing advantages for industrial applications. Each part of the sandwich core structures with auxetic core configurations was printed separately and then bonded using an epoxy-based adhesive. To evaluate the mechanical performance of the proposed bonded sandwich structures, three-point and four-point bending tests with DIC (Digital Image Correlation) analyses were conducted. The bending test results of adhesively bonded sandwich structures were compared with those of monolithic sandwich structures and the effectiveness of the proposed innovative production method was evaluated. Re-entrant, star-shaped, and V-shaped auxetic core configurations were compared in terms of the bending performances of the adhesively bonded and monolithic sandwich structures. Monolithic and adhesively bonded sandwich structures showed similar bending behavior as far as load-carrying capacity, deformation stages, and crashworthiness performance are concerned based on three and four-point bending tests. Hence, the proposed innovative production approach can be applied to sandwich structures to enhance their repairability and support sustainable manufacturing.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 4
    Polarisation Over the Meaning of Democracy: The Case of Political Parties in Turkey
    (Sage Publications Ltd, 2023) Akboga, Sema; Sahin, Osman; Arik, Engin
    As the primary means of political organisation, political parties remain vital to contemporary democracies, making it important to investigate their understanding of democracy. This study explores the themes with which five largest political parties in Turkey associate democracy. We studied tweets posted by official accounts of these parties' headquarters and branches, as well as by other Twitter accounts that are institutionally linked to these parties. We found significant differences between the government bloc and the opposition bloc as well as between People Alliance and Nation Alliance in terms of the themes with which they associate democracy. The government bloc and People Alliance use themes such as national will and military coups while referring to democracy. The opposition bloc and Nation Alliance emphasise themes such as equality, freedom of the press, and justice. We conclude that parties' and blocs' different attitudes towards democracy are indicators of political polarisation in Turkey.