Atahan, Mithat Gökhan
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Atahan, M. Gokhan
Atahan, Mithat Gokhan
MG Atahan
Atahan, Mithat Gokhan
MG Atahan
Job Title
Dr. Öğr. Üyesi
Email Address
mithatgokhan.atahan@agu.edu.tr
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02.06. Makine Mühendisliği
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Current Staff
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Sustainable Development Goals
13
CLIMATE ACTION
0
Research Products
17
PARTNERSHIPS FOR THE GOALS
0
Research Products
8
DECENT WORK AND ECONOMIC GROWTH
0
Research Products
9
INDUSTRY, INNOVATION AND INFRASTRUCTURE
5
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12
RESPONSIBLE CONSUMPTION AND PRODUCTION
3
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16
PEACE, JUSTICE AND STRONG INSTITUTIONS
0
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11
SUSTAINABLE CITIES AND COMMUNITIES
0
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1
NO POVERTY
0
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6
CLEAN WATER AND SANITATION
0
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10
REDUCED INEQUALITIES
0
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14
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0
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15
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0
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5
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0
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4
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0
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7
AFFORDABLE AND CLEAN ENERGY
0
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3
GOOD HEALTH AND WELL-BEING
2
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2
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0
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Documents
13
Citations
117
h-index
7
Documents
13
Citations
113
Scholarly Output
13
Articles
13
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347/32
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0
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0
WoS Citation Count
112
Scopus Citation Count
117
WoS h-index
7
Scopus h-index
7
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0
Projects
1
WoS Citations per Publication
8.62
Scopus Citations per Publication
9.00
Open Access Source
0
Supervised Theses
0
| Journal | Count |
|---|---|
| Journal of Adhesion Science and Technology | 4 |
| Engineering Failure Analysis | 2 |
| Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications | 2 |
| Applied Composite Materials | 2 |
| Journal of Aerospace Engineering | 1 |
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13 results
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Now showing 1 - 10 of 13
Article Citation - WoS: 9Citation - Scopus: 9Low Velocity Oblique Impact Behavior of Adhesively Bonded Single Lap Joints(Taylor & Francis Ltd, 2019) Atahan, M. Gokhan; Apalak, M. Kemal; Atahan, M. Gokhan; Apalak, M. KemalThis article addresses the low velocity oblique impact behavior of adhesively bonded single lap joints, and the effects of adherend strength and plastic ductility, impact energy, overlap length and oblique impact angle on the damage initiation and propagation in the adhesive layer. The experimental contact force-time, contact force-central displacement variations, axial separation lengths through the adhesive layer and permanent central deflections of overlap region, adhesive fracture surfaces were evaluated in detail. In the explicit finite element analyses, the adhesive layer was divided into three zones: upper and lower adhesive interfaces and the adhesive layer between these interfaces. The adhesive interfaces were modeled with cohesive zone approach to predict the failure initiation and propagation along both upper and lower adhesive-adherend interfaces, whereas the elastic-plastic material model was implemented for the middle adhesive region between the upper and lower adhesive interfaces. The proposed finite element model predicted reasonably the damage initiation and propagation through the adhesive layer, and the contact force-time/central displacement variations. Especially, the test and analysis results were compared with those of the adhesively bonded single lap joints under a normal transverse impact load. Increasing oblique impact angle resulted in lower peak contact forces, shorter contact durations and earlier damage initiation and propagation through the adhesive layer. The peak contact forces increased, the contact duration decreased with increasing impact energy. The strength and plastic deformation capability of adherend materials also affected the damage initiation and propagation through the adhesive layer as well as the after-impact joint geometry.Article Citation - WoS: 12Citation - Scopus: 12Low-Speed Bending Impact Behavior of Adhesively Bonded Single-Lap Joints(Taylor & Francis Ltd, 2017) Atahan, M. Gokhan; Apalak, M. KemalThis study addresses the low-speed impact behavior of adhesively bonded single-lap joints. An explicit dynamic finite element analysis was conducted in order to determine the damage initiation and propagation in the adhesive layers of adhesive single-lap joints under a bending impact load. A cohesive zone model was implemented to predict probable failure initiation and propagation along adhesive-adherend interfaces whereas an elasto-plastic material model was used for the adhesive zone between upper and lower adhesive interfaces as well as the adherends. The effect of the plastic deformation ability of adherend material on the damage mechanism of the adhesive layer was also studied for two aluminum materials Al 2024-T3 and Al 5754-0 having different strength and plastic deformation ability. The effects of impact energy (3 and 11 J) and the overlap length (25 and 40 mm) were also investigated. The predicted contact force-time, contact force-central displacement variations, the damage initiation and propagation mechanism were verified with experimental ones. The SEM and macroscope photographs of the adhesive fracture surfaces were similar to those of the explicit dynamic finite element analysis.Article Citation - WoS: 1Citation - Scopus: 2Compression Performance of 3D-Printed Ant-Inspired Lattice Structures: An Innovative Design Approach(Sage Publications Ltd, 2025) Atahan, Mithat Gokhan; Saglam, SelmanIn 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: 5Citation - Scopus: 5Low-Speed Bending Impact Behaviour of Adhesively Bonded Dissimilar Single-Lap Joints(Taylor & Francis Ltd, 2022) Atahan, M. Gokhan; Apalak, M. KemalThis study investigates the low-speed bending impact behaviour of adhesively bonded dissimilar single-lap joints and the effects of both strength and plastic deformation capability of adherend material on adhesive failure. Dissimilar adhesive single-lap joint specimens, such as Al 2024-T3 (top adherend)-Al 5754-0 (bottom) and Al 5754-0 (top)-Al 2024-T3 (bottom), were tested at two impact energy levels (3 and 11 J) for two overlap lengths (25 and 40 mm). The progressive failure analysis of the adhesive layer was also conducted by the non-linear explicit finite element method. The adhesive layer was modelled with a 3D cohesive layer along with the upper and lower adhesive interfaces and a non-linear continuum adhesive region between two cohesive layers. The continuum adhesive region had elasto-plastic adhesive properties whilst the cohesive layers obeyed 3D cohesive rules. The experimental and predicted contact force-time, contact force-displacement diagrams, axial separation lengths of the failed adhesive region, permanent deflection of the bonded region, fracture surfaces were in good agreement. The strength and plastic deformation capability of adherend materials and impact energy levels affected the progressive adhesive failure behaviour. The proposed finite element model was successful reasonably in predicting the initiation and propagation of the adhesive failure.Article Citation - WoS: 11Citation - Scopus: 11Experimental Investigation of Oblique Impact Behavior of Adhesively Bonded Composite Single-Lap Joints(Springer, 2022) Atahan, M. Gokhan; Apalak, M. KemalDetermining the impact behavior of adhesive joints allows the designing of high-strength joints. Therefore, the dynamic behavior of adhesive joints has recently become a trending research topic. The study aims to examine the impact behavior and damage mechanism of the adhesively bonded composite joints, taking into account different impact angles. The mechanical behavior of adhesively bonded glass-fiber reinforced laminated composite single-lap joints under bending impact load was experimentally determined via a drop weight impact test machine. The effects of impact angle (theta = 0 degrees, 10 degrees, 20 degrees, 30 degrees), fiber angle (phi = 0 degrees, 45 degrees, 90 degrees), and overlap length (b = 25, 40 mm) on the impact behavior of the joints were investigated. These parameters were determined to affect the impact behavior of the joint and the damage characterization. The highest contact force occurred in the joints with 0 degrees fiber angle having the highest bending strength, and the lowest contact force occurred in the joints with 90 degrees fiber angle having the lowest bending strength. Due to the increase in the impact angle, the maximum contact force value in the joints decreased, while the total contact time increased. The increase in overlap length had little effect on the maximum contact force and total contact time, and the vertical displacement decreased due to the increasing bending stiffness. The unbalanced joint with 45 degrees fiber angle was forced to rotate around its axis due to in-plane unbalanced shear stress distributions induced by the bending impact load. The unbalanced shear stress distribution caused shear damage at the fiber-matrix interface and the top composite-adhesive interfaces. In joints with 0 degrees fiber angle, the impact energy was mostly met with adhesive damage, while the composite adherend was damaged as a result of increased shear stresses in the matrix region for the joints with 90 degrees fiber angle.Article Citation - WoS: 14Citation - Scopus: 17Comparative Study on Bending Behavior and Damage Analysis of 3D-Printed Sandwich Core Designs With Bio-Inspired Reinforcements(Pergamon-Elsevier Science Ltd, 2024) Atahan, M. Gokhan; Erikli, Merve; Ozipek, Enes; Ozgun, FulyaIn this study, novel sandwich core designs with bio-inspired reinforcements were proposed and their bending behaviors were comparatively examined. The geometrical shapes of alligator osteoderm and chambered nautilus shell were utilized as bio-inspired reinforcements for sandwich core structures. Sandwich core structures were produced through the additive manufacturing method. Experimental tests and finite element analysis were performed to determine the bending performances of the proposed sandwich core structures. The loadcarrying capacity, deformation ability, damage-tolerant capability, energy absorption, and damage mechanisms of the proposed sandwich core structures were comparatively investigated through experimental and numerical methods. The orthotropic material model and Hashin's damage criterion were used in the numerical model of 3D-printed sandwich core structures to consider the effect of the filament raster orientation on the elastic and damage behavior of the sandwich core structures. Compared to the classical honeycomb sandwich core structure, while bio-inspired reinforcements improved the load-carrying capacity and damage-tolerant capability of sandwich core structures, they reduced the energy absorption ability of sandwich core structures due to reducing the vertical deformation ability of sandwich core structures. Bio-inspired reinforcements significantly affected the stress distribution and damage behavior of the sandwich core structures. They reduced von Mises stress level at the outer cell edges of the sandwich core structures and caused reinforcement damage instead of outer cell damage.Article Citation - WoS: 2Citation - Scopus: 3Comparative 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) Atahan, Mithat Gokhan; Sevim, Caglar; Demirbas, Munise Didem; Apalak, Mustafa KemalThe 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 - Scopus: 1Effect 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) Atahan, M. Gokhan; Zeybek, HalilRecent 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: 10Citation - Scopus: 11Finite Element Analysis of Low-Speed Oblique Impact Behavior of Adhesively Bonded Composite Single-Lap Joints(Springer, 2023) Atahan, M. Gokhan; Apalak, M. KemalThe 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.Article Citation - WoS: 4Citation - Scopus: 3Low-Speed Oblique Impact Response of Adhesively Bonded Dissimilar Single-Lap Joints(ASCE-Amer Soc Civil Engineers, 2022) Atahan, M. Gokhan; Apalak, M. KemalAdhesively bonded joints are widely preferred for joining similar and dissimilar materials due to the mechanical advantages they provide. As the demand for the adhesively bonded method increases, it is necessary to determine the behavior of joints under impact loads for joint design. The aim of this study was to investigate the low-speed oblique impact behavior of dissimilar single-lap joints and the effect of plastic deformation ability and strength of the adherends [(Top) Al 2024-T3-(Bottom) Al 5754-0, (Top) Al 5754-0-(Bottom) Al 2024-T3], overlap lengths (25, 40 mm), and impact energy (3, 11 J) on adhesive damage. The behavior of the joints determined by the numerical model under low-speed oblique impact was compared with experimental results. Considering the contact force-time, contact force-displacement, and adhesive damage, the numerical model was reasonably compatible with the experimental results. The damage initiation and propagation in the adhesive layer were determined by three-dimensional explicit finite-element analysis. In order to obtain suitability for the damage mechanism by observing the experimental bonding damage surfaces, the adhesive region was divided into three zones, the upper and lower adhesive interfaces and a middle adhesive layer between them. The different strength and plastic deformation ability of the adherends had a significant effect on the adhesive damage initiation and propagation. In the case of high strength and low deformation ability of the adherend material (Al 2024-T3) contacting with the impactor, a reduction of the adhesive damage occurred due to the deformation of the adherend material (bottom adherend) with low strength and high deformation capability. The oblique impact load and the different mechanical properties of the adherends greatly affected the adhesive damage initiation and propagation of single-lap joints.
