Browsing by Author "Atahan, Mithat Gokhan"

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Compression performance of 3D-printed ant-inspired lattice structures: An innovative design approach
(Sage Journals, 2025) Atahan, Mithat Gokhan; Saglam, Selman; 0000-0002-8180-5876; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; 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.
Finite Element Analysis of Low-Speed Oblique Impact Behavior of Adhesively Bonded Composite Single-Lap Joints
(SPRINGER, 2023) Atahan, Mithat Gokhan; Apalak, M. Kemal; 0000-0002-8180-5876; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Atahan, Mithat Gokhan
The development of a realistic numerical model that predicts the impact behavior of adhesively bonded composite joints is important for many industrial sectors such as automotive, aerospace, and marine. In this study, it was aimed to develop a numerical model that can predict the low-velocity oblique impact behavior of composite single-lap joints close to the experimental results. The validation of the proposed numerical model was carried out with the results of the previously experimentally tested joints. In explicit finite element analysis, the orthotropic material model and Hashin's damage criterion were used in the numerical model of composite adherends. The adhesive region was divided into three different regions. The cohesive zone model (CZM) was used to determine the damage initiation and propagation in the upper and lower interface regions of adhesive. The middle region of the adhesive between the two cohesive interfaces was modeled with an elastic-plastic material model to reflect the plastic material behavior of the adhesive in the analysis. The effects of impact angle, fiber orientation, and overlap length on adhesive damage initiation and propagation were investigated in detail. There is a good agreement between the numerical and experimental results, considering the contact force-time variations and composite and adhesive damage. The impact angle and fiber angle had a significant effect on the impact behavior of the composite joints and the adhesive damage initiation and propagation. The increase in impact angle and fiber angle caused a decrease in the maximum contact force value. Adhesive damage propagation patterns varied according to the composite fiber orientation. In addition, since the shear toughness of the adhesive is higher than its tensile toughness, the amount of adhesive damage and damage propagation rate decreased as the impact angle increased.