Browsing by Author "Gultekin, Kursat"

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The Effect of Moment and Flexural Rigidity of Adherend on the Strength of Adhesively Bonded Single Lap Joints
(Taylor & Francis Ltd, 2015) Gultekin, Kursat; Akpinar, Salih; Otzel, Adnan
In the present study, mechanical properties of different single lap joint configurations derived from adherends with different thicknesses subjected to tensile loading were investigated experimentally and numerically. For this purpose, experimental studies were conducted on two different types of SLJ samples, the first type with identical upper and lower adherend thicknesses and the second with different upper and lower adherend thicknesses. For the first type, five different thickness values were tested. For the second type, the lower adherend thickness was constant while five different upper adherend thickness values were tested. The adhesive was prepared from a two-part paste. After the experimental studies, stress analyses on the SLJs were performed with three-dimensional finite element analysis by considering the geometrical non-linearity and the material non-linearities of the adhesive (DP460) and adherend (AA2024-T3). It was observed that, in single lap joint geometry, variation in the thickness of the adherend and the use of lower and upper adherends with different thickness values changed the stress concentrations at the edges of the overlap regions, affecting the experimental failure load of the joints.
The Effect of the Adherend Width on the Strength of Adhesively Bonded Single-Lap Joint: Experimental and Numerical Analysis
(Elsevier Sci Ltd, 2014) Gultekin, Kursat; Akpinar, Salih; Ozel, Adnan
In the present study, mechanical properties of different Single Lap Joint (SLJ) configurations with different adherent width values subjected to tensile loading were investigated experimentally and numerically. Using AA2024-T3 aluminum alloy as adherend and DP460 as paste adhesive, eight different types of single-lap joint samples (width of the adherent was 5, 10, 15,20 or 25 m; overlap length was 5,10, 15, 20 or 25 mm) were produced for experimental studies. Stress analyses in the SLJ were performed non-linear finite element method by considering the geometrical non-linearity and the material non-linearities of the adhesive (DP460) and adherend (AA2024-T3). As a result, in SLJ geometries, increasing the adherent width raises the load-carrying capacity of the joints higher when compared to increasing overlap length. The failure load value of the joint increases as the area of bonding varies from rectangle to square. In addition, it was found that the data obtained from finite element analysis were coherent with experimental results. (C) 2014 Elsevier Ltd. All rights reserved.
The Effects of Graphene Nanostructure Reinforcement on the Adhesive Method and the Graphene Reinforcement Ratio on the Failure Load in Adhesively Bonded Joints
(Elsevier Sci Ltd, 2016) Gultekin, Kursat; Akpinar, Salih; Gurses, Ahmet; Eroglu, Zafer; Cam, Salim; Akbulut, Hamit; Ozel, Adnan
This study experimentally determines the tensile failure load of the nanocomposite adhesive - obtained by adding nanostructures to the adhesive - using four different methods in single-lap joints. For the study, adhesively bonded single-lap joints were produced by using DP460 liquid structural epoxy as the adhesive, AA2024-T3 aluminum alloy as the adherend and graphene as the nanostructure. When the failure load obtained from the experiments was examined, it was seen that, while the nanostructure-reinforced methods indicated in the literature have a great effect on the failure load of the joint and the standard deviation, a new method developed in this study increased the failure load of the joint and minimized the standard deviation. These improvements increased the reliability and reproducibility of the joint. (C) 2016 Elsevier Ltd. All rights reserved.
Experimental Analysis on the Single-Lap Joints Bonded by a Nanocomposite Adhesives Which Obtained by Adding Nanostructures
(Elsevier Sci Ltd, 2017) Akpinar, Idal Avinc; Gultekin, Kursat; Akpinar, Salih; Akbulut, Hamit; Ozel, Adnan
Especially findings from nanoscience and nanotechnology, which have progressed significantly in recent years, influence materials and mechanical sciences deeply as well as other disciplines. In this study, the failure loads of single-lap joints (bonding joints used in space, automotive and aerospace applications) bonded by a nanocomposite adhesive obtained by adding nanostructure to the adhesive were experimentally examined to increase the failure load of adhesively bonded joints. Adhesively bonded single-lap joints were produced using DP460 toughened adhesive type, DP270 rigid adhesive type and DP125 flexible adhesive type as the adhesives; AA2024-T3 aluminum alloy was used as the adherend, and Graphene-COOH, Carbon Nanotube-COOH and Fullerene C60 were used as the added nano structures. Furthermore, to examine the effects of nanostructure reinforcement ratios in the adhesive at joint-failure load, three nanostructures with different ratios of 0.25%, 0.5%, 1%, 2% and 3% were added. As a result, when the experimental failure loads were examined, the nanocomposite adhesives obtained by adding nanostructure were found to have increased the load failure of the joint. However, increase rate in the failure load changes depending on the structural features of the adhesive and the type of nano structure. Moreover, in the geometries of single-lap joints produced in this study, the best nanostructure reinforcement ratio, in terms of the failure load of the joint, was 1% percent by weight. (C)2016 Elsevier Ltd. All rights reserved.
An Experimental Study on Composite Adhesives Reinforced with Different Types of Organo-Clays
(Taylor & Francis Ltd, 2018) Akpinar, Iclal Avinc; Gultekin, Kursat; Akpinar, Salih; Gurses, Ahmet; Ozel, Adnan
In this study, the mechanical properties of single lap joints prepared by adding nanoclays with different properties into adhesives with different characteristics (toughened, flexible, paste-type, and rigid) were experimentally investigated. Single lap joints and bulk specimens were produced using DP460, DP125, Araldite 2015, and AV138 as adhesives. High-concentration hydrocarbon-doped organo-clay (HDOC-1) obtained from Cankiri, low-concentration hydrocarbon-doped organo-clay (HDOC-2) obtained from Erzurum, and organo-clay (OC) were incorporated into the adhesives as reinforcements at two different concentrations (1% and 2% wt.). The aluminum alloy AA2024-T3 was used as the adherend material. Evaluation of experiment results showed that both the characteristics of the adhesive (toughened, flexible, paste-type, and rigid) and the different forms of clays significantly influenced failure loads of the joints. Moreover, increasing or decreasing the amount of clay added into the adhesive also affected failure loads of the joints; 1% wt. reinforcement provided the best results.
Investigation of Mechanical and Thermal Properties of Nanostructure-Doped Bulk Nanocomposite Adhesives
(Taylor & Francis Ltd, 2018) Akpinar, Iclal Avinc; Gurses, Ahmet; Akpinar, Salih; Gultekin, Kursat; Akbulut, Hamit; Ozel, Adnan
In recent years, findings in nanoscience and nanotechnology have deeply influenced many disciplines including the material and mechanical sciences. Polymers including nanostructures have attracted attention as their adoptions in general engineering composites have yielded efficient results. In this study, three different two-component (epoxy-hardener) adhesives were doped with graphene nanoplatelets, graphene oxide nanoplatelets, carbon nanotube, and fullerene C60 at three different rates (0.5%, 1%, and 2% by weight) and the mechanical and thermal properties of the nanocomposite adhesives were examined. The nanocomposite adhesives' mechanical properties were analyzed via tensile tests and thermal properties were analyzed via Differential Scanning Calorimeter (DSC) thermograms and Fourier Transform Infrared Spectroscopy (FT-IR) spectra. Results showed that doping nanostructures improve the stress-strain capacity of the adhesives. Both mechanical and thermal properties of the nanocomposite adhesives seem to change depending on the amount of nanostructure. Additionally, DSC and FT-IR curves showed an agreement with these improvements in the adhesives' mechanical properties.
Research on Strength of Nanocomposite Adhesively Bonded Composite Joints
(Elsevier Sci Ltd, 2017) Akpinar, Iclal Avinc; Gultekin, Kursat; Akpinar, Salih; Akbulut, Hamit; Ozel, Adnan
Due to their great advantages, adhesively bonded joints are frequently used in many areas like automotive, marine, space and aerospace industries. Especially findings from nanoscience and nanotechnology, which have progressed significantly in recent years, influence adhesives sciences significantly as well as other disciplines. In the present study, nanoparticles were added to the adhesive to increase the damage load of adhesively bonded single lap composite joints and tensile and bending moment damage loads of these joints were experimentally investigated. In the study, carbon fiber fabric reinforced composites (0/90 degrees) with Plain Weave were used as the adherend; rigid, tough and flexible adhesive types were used as the adhesive and 1 wt% Graphene-COOH, Carbon Nanotube-COOH and Fullerene C60 were used as the nanoparticles. As a result, based on the AA2024-T3 aluminum alloy used in a study conducted by Akpinar et at. [1], the use of carbon fiber fabric reinforced composites as the adherend considerably increases the damage load of the joint, depending on the adhesive type. Moreover, when failure loads obtained from experiments were examined, the addition of nanoparticles to the adhesive was shown to increase the tensile and four-point bending damage load of joint, depending on the adhesive and nanoparticle type. (C) 2017 Elsevier Ltd. All rights reserved.