Browsing by Author "Ardahanli, Metehan"

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Design, Fabrication, and Mechanical Analysis of Auxetic Cementitious Tubular Composites: An Experimental and Numerical Study
(Elsevier Sci Ltd, 2025) Solak, Kemal; Orhan, Suleyman Nazif; Kotan, Turkay; Ardahanli, Metehan
Auxetic cementitious composites exhibit enhanced mechanical performance such as high energy dissipation capacity and crack resistance. Such characteristics position them as promising materials for advanced construction applications. This study investigates the design, fabrication, and mechanical performance of novel auxetic cementitious tubular composites under quasi-static compressive loading. Auxetic cementitious tubular composites (ACTCs) were fabricated by casting glass fiber-reinforced mortar into a 3D-printed auxetic tubular mold. A combination of experimental and numerical methods was employed, including uniaxial compression tests, digital image correlation (DIC), and finite element modeling (FEM). This study further conducted a parametric analysis to examine the effects of geometric parameters, including wall thickness, porosity, and height, as well as varying loading conditions, on the failure mechanisms, stress-strain behavior, Poisson's ratio, and energy absorption characteristics of ACTCs. Experimental and numerical results confirmed the auxetic behavior of ACTCs under compressive loading. The stress-strain response exhibited distinct phases, including elastic deformation, peak stress, and post-peak softening. Failure mechanisms were primarily governed by plastic strain concentration, crack propagation, and densification. Cracks initially formed at the minor axis ends of elliptic perforations and propagated with increasing strain. FEM simulations accurately captured deformation behaviors and mechanical responses, aligning closely with experimental findings, while DIC analysis validated strain localization patterns. Parametric analysis results indicated that increased wall thickness enhanced peak stress and energy absorption, while porosity adjustments influenced both load-bearing capacity and auxeticity. The developed ACTC presents a novel design approach, proving its feasibility and exhibiting substantial potential for engineering applications.
Resistance of Some Outdoor Pavements to Destructive Combined Effects in Cold Regions
(Taylor & Francis Ltd, 2024) Kotan, Turkay; Ardahanli, Metehan
This study aims to investigate some physical and mechanical properties and resistance to triple-combined effect (abrasion, freeze-thaw and de-icing salt) of Interlocking concrete block pavement (ICBP), concrete cube pavement (CCP), concrete kerb (CK) and natural basalt stone pavement (BSP) products. The pavement products were supplied in different types/varieties from manufacturers in Erzurum-Turkey. The Bohme abrasion test was performed at the end of every 5 cycles with NaCl solution freeze-thaw cycles in addition to the physical and mechanical tests, which are important in applications. As a result, while the BSP and CK concrete pavements completed a total of 60 cycles without disintegrating with the least mass loss against the triple-combined effect, the concrete cube pavement-colourless (CCP-C) product disintegrated in the shortest time. It was determined that there can be significant differences in the mechanical and durability properties of the same type of ICBP products from different manufacturers. It was seen that the use of iron oxide-based pigments and colour type positively affect the mechanical and durability properties of Dry-cast Concrete (DCC) pavements. Additionally, it was determined that there are strong positive relationships between the durability performance of pavements and their compressive strength and Schmidt values, and negative relationships with their porosity.