Pamukkale University Journal of Engineering Sciences

281-286

Authors: Tevfik Küçükömeroğlu, Hasan Yılmaz, Semih Mahmut Aktarer

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. Key words: Nomex, Sandwich, Stiffness, Failure modes, Fatigue model.

293-297

Authors: Miroslaw Sebastian Bonek

ABSTRACT: 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. Key words: Tool steels, Laser alloying, Surface engineering.

303-309

Authors: Eray Sabancı, Ramazan Karakuzu

ÖZET: 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. Anahtar Kelimeler: Tabakalı kompozitler, gömülü delaminasyon, darbe davranışı. ABSTRACT: 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. Key words: Laminated composites, Embedded delamination, Impact behavior.

319-322

Authors: Yelda Akçin, Osman Asi, Önder Yeşil

ÖZET: 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. Anahtar Kelimeler: Cam elyafı, Karbon elyafı, Kompozit malzeme, Sert seramik tozları, Plazma sprey kaplama. ABSTRACT: 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. Key words: Glass fiber, Carbon fiber, Composite material, Hard ceramic powder, Plasma spray coating.