The aim of the paper was to optimize the Selective Laser Sintering (SLS) and co-firing in the infrared conveyor furnace parameters in front Screen Printed (SP) contacts. The co-firing in the infrared conveyor furnace was carried out at various temperature. The SLS was carried out at various a laser beam, scanning speed of the laser beam and front electrode thickness. The investigations were carried out on monocrystalline silicon wafers. During investigations was applied a silver powder with the grain size of 40 μm. The contacts parameters are obtained according to the Transmission Line Model (TLM) measurements. Firstly, this paper shows the comparison between the convectional an unconventional method of manufacturing front contacts of monocrystalline silicon solar cells with the different morphology of silicon for comparative purposes. Secondly, the papers shows technological recommendations for both methods in relation to parameters such as: the optimal paste composition, the morphology of the silicon substrate to produce the front electrode of silicon solar cells, which were selected experimentally in order to produce a uniformly melted structure, well adhering to the substrate, with the low resistance of the front electrode-to-substrate joint zone.

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In this study AA5754 and A6061 alloys have been butt welded to each other by using friction stir welding (FSW). At constant tool geometry and tool angle experiments were carried out, joints were performed using different welding speed, rotation speed and especially tool press force. The mechanical properties of the welded samples were determined by using tensile test, bending test and micro hardness. Generated microstructure and hardness profile was obtained in the welding zone. In this friction stir welding study the parameters which affect the joint structure are the tool press force, welding speed and tool rotation speed which were determined. At the end of study it is determined that AA5754 and AA6061 alloys can be successfully welded by using Friction Stir Welding method under different tool press forces at least 6kN.

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The main benefits of using the sandwich concept in structural components are the high stiffness, good fatigue resistance and low weight ratios. Recent advances in materials and construction techniques have resulted in further improvement and increased uniformity of the sandwich composite properties. In order to use these materials in different applications, the knowledge of simply their static properties alone is not sufficient but additional information on their fatigue properties and durability are required. In this paper, first static and fatigue tests on four points bending of nomex honeycomb composite sandwich panels have been performed. Load/displacement and S-N fatigue curves are presented and analysed. Fatigue failure and damage modes are observed with an optical microscope and are discussed. The second is to address such fatigue behaviour by using a damage model and check it by experimentation. This fatigue damage model is based on stiffness degradation, which is used as a damage indicator. Two non-linear cumulative damage models derived from the chosen stiffness degradation equation are examined with assumption of linear Miner’s damage summation. Predicted results are compared with available experimental data.

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The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as alloying material, and their influence on structure and chemical composition of the steel. Analysis of the process conditions influence on thicknesses of the alloyed layer and heat-affected zone is presented.

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This study aims to examine the effect of interface crack on the free vibration response of a sandwich composite beam experimentally and numerically. Natural frequencies in a thin sandwich composite cantilever beam with root crack are determined. The crack with various lengths is opened between the face sheet and foam core, such as 50, 100, 150 and 200 mm. Free vibration tests of these samples are carried out. For the numerical analysis, ANSYS finite element software is used. Results obtained by numerical analyses and experiments are compared and it is seen that there is a good agreement between them.

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Bu çalışma da, yapay delaminasyonun konumunun ve boyutunun, tabakalı kompozit malzemelerin darbe davranışları üzerine etkisi deneysel olarak incelenmiştir. Deney numuneleri, vakum destekli reçine infüzyon metodu kullanılarak delaminasyonlu ve delaminasyonsuz olarak üretilmiştir. Deneylerde CEAST-Fractovis plus test cihazı kullanılmıştır. Deney sonucu olarak delaminasyon konumunun, delaminasyon boyutuna göre daha etkili olduğu gözlemlenmiştir.

In this study, the influence of size and location of embedded delamination on impact behavior of laminated composite was investigated, experimentally. The specimens were produced as for with and without delamination by vacuum assisted resin infusion molding method (VARIM). CEAST-Fractovis plus impact test machine was used in the experiments. As a result of the experiments, the location of delamination on the impact behavior was seen to be more effective than the size of delamination.

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Bu çalışmada üç boyutlu kıvrımsız dokuma karbon-epoksi kompozitlerin dinamik çekme yüklemesi altında yorulma özellikleri tespit edilmiştir. Atkı doğrultusundan alınmış numuneler için sonsuz yorulma yük seviyesi 27.5 kN olarak tespit edilmiştir. Yorulma yüklemesi altında kompozit malzeme içinde hasarın z-ipliklerinin atkı iplikleri ile kesiştikleri kısımlarda başladığı ve buradan yayıldığı anlaşılmıştır. Üç boyutlu dokuma yapıda z-iplikleri iplik katmanlarını bir arada tuttuğu için, klasik iki boyutlu kompozitlerde meydana gelen delaminasyon hasarları meydana gelmemiştir. Bu durum kompozit malzeme modülü ve yük taşıma kapasitesinin iki boyutlu klasik kompozitlere göre daha üstün ve sürdürülebilir olduğunu göstermektedir.

This paper reports results of study of fatigue behavior of a non-crimp 3-dimensional woven carbon/epoxy composite in tension-tension fatigue. Infinite fatigue life limit corresponds to the load of 27.5 kN for fill direction. The damage under fatigue loading starts and develops from intersection of z-yarns and fill yarns. Since the z-yarns bonded the yarn layers, it is not seen the delaminastion damages. This indicate that for load carrying capacity and stiffness of 3-dimensional composites better than classic 2-dimensional textile composites.

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Kompozit malzemeler günümüzde, yüksek dayanım/yoğunluk ve yüksek elastisite modülü/yoğunluk oranının önemli olduğu savunma sanayinde, deniz taşımacılığında, otomotiv ve uzay sektöründe çok yaygın olarak kullanılmaktadır. Ancak tribolojik davranışları ve düşük aşınma dirençleri gibi yüzey özellikleri ile ilgili nedenlerden dolayı kullanım alanları sınırlanmaktadır. Malzemelerin bu özelliklerinin iyileştirilebilmesi için yapılacak çalışmalardan en önde geleni ise kaplamadır. Bu çalışmada, günümüzde yaygın olarak kullanılmaya başlanılan plazma sprey kaplama yöntemi ile sert seramik tozları (Al2O3+TiO2 ve CrO3 ) cam elyaf takviyeli ve karbon elyaf takviyeli epoksi matrisli kompozit malzemelerin yüzeyine kaplama işlemi yapılmış ve elde edilen kaplamaların fiziksel, mekaniksel ve metalografik özellikleri incelenmiştir.

Nowadays, composite materials are widely used in the sectors that are overrated high strength / density and high elasticity modulus / density ratios such as defense industry, marine transportation, automotive and aerospace industry. However, because of the surface properties such as tribological behavior and low wear resistance their application areas are limited. Coating is the prominent process in order to improve these properties of the materials. In this study, hard ceramic powders (Al2O3 + TiO2 and CrO3) are coated to surface of glass fiber and carbon fiber reinforced epoxy matrix composite materials with plasma spray coating method started to be widely used todays and physical, mechanical and metallographic properties of obtained coatings were examined.

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