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Purpose This study aims to systematically compare the effect of increasing fiber–matrix interface adhesion and matrix toughness in layered composite materials. Design/methodology/approach Silane ((3-glycidyloxypropyl) trimethoxysilane) was applied to strengthen the fiber–matrix interface connection in e-glass/epoxy laminated composite material. Using a cationic surfactant, 0.1% multi-walled carbon nanotubes (CNTs) were added to the matrix in two different ways, by with and without chemical functionalization using the vacuum infusion method. Findings In the results obtained from the three-point bending test specimens, it was determined that the synergistic effect of silane application and non-functionalized CNT in the matrix was higher in terms of flexural modulus and strength values. Practical implications The functionalization of multi-walled CNT did not give the expected results because of reasons such as viscosity increase and agglomeration in the matrix. Originality/value In this study, a simple model for normalization and prediction purposes was developed, which allows the determination of the flexural modulus and un-notched flexural strength values from one test result of the notched specimen. A systematic comparison was performed by varying each parameter in the composite material.

Günlük hayatımızda ve bilimsel araştırmalarda gerçeğe yakın ve gürültüsüz görüntülere olan ihtiyaç artmaktadır. Ancak görüntüler, gürültü ile bozulmakta ve bu da görsel görüntü kalitesinin düşmesine neden olmaktadır. Bu nedenle, görüntü özelliklerini kaybetmeden gürültüyü azaltmak için çalışmalar yapılmaktadır. Şimdiye kadar, gürültüyü azaltmak için çeşitli yöntemler önerilmiş olup, her yöntemin farklı avantajları bulunmaktadır. Bu makalede, alanında en iyi sonucu elde eden yöntemler hakkında bilgi verilerek, video ve sabit görüntülerinde gürültü azaltma alanında yapılan geleneksel gürültü giderme yöntemleri ve derin öğrenme yöntemlerine ait çalışmalar özetlenip, elde edilen sonuçlar birbirleriyle karşılaştırılmaktadır. Yapılan araştırmalar deneylerin toplamsal beyaz Gauss gürültüsü durumuna odaklandığını göstermektedir. Görüntülerde gürültü giderme aşamasında zaman içerisinde geleneksel gürültü giderme yöntemleri, makine öğrenmesi yöntemleri, derin öğrenme yöntemleri ve diğer matematiksel yöntemler kullanılmış olup, derin öğrenme yöntemleri daha başarılı sonuçlar elde etmektedir. Ancak elde edilen verilere göre orijinal görüntü çiftlerine sahip olmadan modelin eğitilmesi konusunda çalışmaların yetersiz olduğu ve değişik gürültü seviyelerinde tek bir yöntemin başarılı olamadığı görülmüştür. İleride yapılacak çalışmalarda gerçek hayattaki görüntülerde var olan gürültülerin nasıl giderileceği konusuna daha detaylı odaklanılması gerektiği görülmektedir.

In this study, metal was removed by electro erosion processing method using Copper Chromium Zirconium Alloy Electrode from Sleipner Cold Work Tool Steel with 60-62 HRC hardness value. In this context, experiments were carried out using three different discharge currents (6,25; 12,5; 25 A), three different pulse on times (3; 6; 9 µs), three different pulse off times (4; 6; 8 µs). The effects of the used processing parameters on the fundamental performance outputs such as surface roughness, kerf angle, processing time were determined by analytical measurements and macro analysis. As a result of the analysis, the processing time increased significantly with the increase in the pulse off time and decreased with the increase of the working current and pulse on times. The increase in the working current increased the spark between the workpiece and the electrode, increasing the point melting and evaporation, as a result of which the surface roughness increased. The electrode was worn out due to the effect of the low pulse on time and high pulse off time parameters, as it worked more per unit time, as a result of this wear, the average kerf angle increased. As a result of the % 100 and % 300 increase in the discharge current, the average surface roughness increased by % 62 and % 87, respectively. Failure to evacuate debris and residues caused by wear of both the workpiece and the electrode material during EDM or sticking to electrode tips were caused irregularity in the processing time, surface roughness and kerf formation due to electrode wear., Bu çalışmada 60-62 HRC sertlik değerine sahip Sleipner Soğuk İş Takım Çeliğinden Bakır Krom Zirkonyum Alaşımı Elektrot kullanılarak elektro erozyon işleme (EEİ) yöntemi ile talaş kaldırılmıştır. Bu kapsamda üç farklı boşalım akımı (6,25; 12,5; 25 A), üç farklı ark süresi (3; 6; 9 µs), üç farklı bekleme süresi (4; 6; 8 µs) işleme parametreleri kullanılarak deneyler gerçekleştirilmiştir. Kullanılan işleme parametrelerinin yüzey pürüzlülüğü, kerf açısı, işleme süresi gibi temel performans çıktıları üzerindeki etkileri analitik ölçümler ve makro analizler ile belirlenmiştir. Yapılan analizler neticesinde bekleme süresinin artması ile işleme süresi büyük ölçüde artmış boşalım akımının ve ark süresinin artması ile azalmıştır. Boşalım akımının artması iş parçası ve elektrot arasında kıvılcımlanmayı arttırarak noktasal erime ve buharlaşma arttırmıştır bunun neticesinde yüzey pürüzlülüğü artmıştır. Düşük ark süresi ve yüksek bekleme süresi elektrotu birim zamanda daha fazla çalıştırarak aşındırmış bu aşınma sonucunda ortalama kerf açısı artmıştır. Boşalım akımının % 100 ve % 300’lük artışı neticesinde ortalama yüzey pürüzlülüğü sırasıyla % 62 ve % 87 oranında artmıştır. EEİ esnasında hem iş parçasının hemde elektrot malzemesinin aşınmasıyla ortaya çıkan debris ve kalıntıların ortamdan tahliye edilememesi veya elektrot uç kısımlarına yapışması işleme süresinde, yüzey pürüzlülüğünde ve elektrot aşınmasına bağlı kerf oluşumunda düzensizliğe sebep olmuştur.

Purpose The purpose of this study is to obtain strong materials with multiwall carbon nanotubes (MWCNTs) doped and investigate laser cut of MWCNTs also find the effect of the laser cutting parameters on composite materials. Design/methodology/approach The laminated composite plates were manufactured by using a vacuum infusion process. The mechanical properties of the composite materials produced were determined according to American Society for Testing and Materials (ASTM) D3039M, ASTM D3171, ASTM D 792 and ASTM D2583. A 130 Watts carbondioxide (CO2) laser cutting machine was used for drilling the two different composite plates with a thickness of 1.6–1.5 mm. Three variables were considered as process parameters including laser power (in three levels of 84.50, 104.00 and 127.40 W), cutting speed (in three levels of 4, 6, 8 mm/s) and 14 mm fixed focal position. Findings The fibers could not be cut due to insufficient melting in the experiments performed using 84.50 and 104.00 W laser power but the cutting was successfully completed when the laser power was 127.40 W. However, as the cutting speed increased, the contact time of the laser beam with the material decreased, so the kerf decreased, but the increased laser power created a thermal effect, causing an increase in hardness around the cutting surface. This increase was lower in MWCNTs doped composites compared to pure composites. It has been found that the addition of nanoparticles to layered glass fiber composite materials played an effective role in the strength of the material and affected the CO2 laser cutting quality. Originality/value This study is a unique study in which the CO2 laser cutting method of MWCNT-doped composite materials was investigated and the machinability without cutting errors, such as delamination, splitting, distortion and burring using the most suitable laser cutting parameters was revealed.

In this study, the holes of glass fiber reinforced polymer (GFRP) and multi-walled carbon nanotubes (MWCNTs) doped GFRP composite materials were drilled using abrasive water jet (AWJ), CO2 laser cutting, orbital drilling, and punching methods; the effects of these methods on hole quality were determined. The hole entry and exit dimensions were obtained equal and in the desired size by orbital drilling; thus, kerf formation was prevented due to the lateral and face milling of the end mill. The surface hardness change was not observed in the hole circles obtained with the orbital drilling and punching methods. However, epoxy hardening was observed in the hole circles obtained by laser cutting due to the heat effect of laser beam. In AWJ method, matrix-fiber integrity was disrupted, and delamination was observed due to the effect of water pressure and kinetic energy; consequently an increase in material thickness was observed and surface hardness decreased. It was determined that MWCNTs additive increased the surface hardness of composites and maintained its hardness and durability in post-cutting measurements. Splintering and burring were not seen in any method, but fiber carbonization was observed in the inner parts of the hole due to thermal effects in laser cutting.

In this study, the effect of adding nanosize additive to glass fiber reinforced composite plates on mechanical properties and surface milling was investigated. In the light of the investigations, with the addition of MWCNTs additive in the composite production, the strength of the material has been changed and the more durable composite materials have been obtained. Slots were opened with different cutting speed and feed rate parameters to the composite layers. Surface roughness of the composite layers and slot size were examined and also abrasions of cutting tools used in cutting process were determined. It was observed that the addition of nanoparticles to the laminated glass fiber composite materials played an effective role in the strength of the material and caused cutting tool wear.

In this paper, meta-heuristic tuning of LQR weighting matrices using various objective functions on the experimental flexible arm under the effects of disturbance is investigated. The use of flexible and lightweight systems provides certain advantages such as high operating speeds, low electricity consumption, and low initial investment costs. However, such systems are more prone to vibration-related problems than their rigid and heavyweight counterparts. One of the closed-loop control methods used to suppress these vibrations is LQR control, but the success of the controller depends on the choice of the gain and regulator matrices. In this study, the Bees algorithm, a meta-heuristic search algorithm, is used to determine LQR matrices. The system performance is compared with similar studies in the literature. The proposed objective function reveals an improvement of 3.1% in rotor maximum overshoot compared to studies in the literature. Flexible link maximum overshoot has been reduced from 17.8 to 7.1%. In order to validate the applicability and repeatability of the proposed method under the noise and disturbance in real systems, experimental verification tests were conducted using the Quanser Flexible Link system. As a result, the proposed method has been experimentally validated and it is estimated that it may well be a very useful controller design approach in various engineering systems and related control system developments.

Nanofibers can be interleaved into polymers and improvements in mechanical properties such as resistance to impact, delamination and debonding as well as enhanced ductility can be obtained. In this work, GFRP laminated composites were interleaved to non-woven nylon 6,6 nanofiber mats which were generated by the electrospinning method. Four kinds of configurations were considered; two pure configurations where GFRP had two and four glass fiber layers and the other two kinds of nanofiber modified configurations that had one and three nylon 6,6 nanofiber mats being interleaved in GFRP. Those specimens were then investigated for their impact resistance, energy absorption and tensile strength capabilities in regard to low-velocity impact and tensile tests. The results showed that adding nylon 6,6 nanofiber mats can increase energy absorption values of the modified specimens, but some decrease in load capacities could be observed.

Endüstride malzemelerin cıvata, perçin ve pim bağlantıları ile montajlanması veya üzerlerine delikler oluşturmak için matkap ile delme yöntemi kullanılmaktadır. Kompozit malzemelerin delinmesi esnasında çapaklanma, delaminasyon ve malzeme yarılması görülmektedir. İşleme parametreleri, delinen malzemenin mekanik özellikleri ve matkap nokta açısı delik kalitesini etkileyen en önemli faktörlerdir. Bu çalışmada cam elyaf takviyeli polimer (CETP) kompozit plakalara nano boyutta katkı maddesi eklenmesinin mekanik özelliklerine ve matkap yöntemi ile delinmesine etkisi araştırılmıştır. Tabakalı cam elyaf kompozit malzemelere nano partikül ilavesinin malzemenin dayanımında etkili bir rol oynadığı ve delik kalitesine etki ettiği görülmüştür. Sabit fener mili devri değerleri kullanılarak yapılan delme işlemlerinde; tezgah ilerlemesi arttıkça çapaklanmanın arttığı, matkap nokta açısının artması ile delik çapının arttığı tespit edildi. 90° ve 140° açılı matkaplar kullanılarak delinen deliklerin çıkış kısımlarında epoksi tabakasının blok şeklinde cam elyaf tabakasından ayrıldığı görüldü.

WOS: 000519806700073, In this study, composites composed of glass fiber reinforced-epoxy laminates interleaved with electrospun polyvinylchloride (PVC) nano-fibres were designed for radar absorption investigations. The laminated composites which were produced in special molds were obtained by placing woven glass fibers between each of PVC nanofiber mats, and the composites were produced in three different forms as pure, multi-walled carbon nanotubes doped and graphene doped. The morphologies of the PVC nanofiber mats were analyzed by scanning electron microscope. The radar absorption efficiencies of the composites in the individual and different combinations were measured in the 3-8 GHz frequency band. Experimental results show that the produced graphene-added composite material has improvable microwave absorption effect at several points in 3-8 GHz band to provide excellent absorption in future studies. The graphene doped structure was found to have a certain absorption characteristic up to 33.82% at a constant frequency. Besides, various strong absorption frequency points have been obtained in the related frequency range. The cascaded graphene doped composite layers can provide broadband absorption for stealth technology.

Bu çalışmada katı yakıtlı alçak irtifa roketi ALP-01’in CAD tasarımı yapılmıştır. 1500 metre irtifa için roket boyutları; seçilen motor için optimize edilmiştir. Burun konisi geometrisi olarak Parabolik tip tercih edilmiş ve uzunluğu 35cm olarak hesaplanmıştır. Burun konisi ve shoulder kısmı için 3D yazıcıda kalıp hazırlanıp cam elyaf malzeme ile elle yatırma yöntemiyle bu kısımlar üretilecektir. Roketimizde iki farklı kurtarma mekanizması kullanılmıştır. Burun konisi, faydalı yük, faydalı yükün paraşütü ve roketin birinci paraşütünün roketten ayrılması için CO2 tüp ile fırlatma mekanizması tasarlanmıştır. Faydalı yükün üzerinde telemetri sistemi olan bir uçuş bilgisayarı bulunmaktadır. Bu bilgisayar yer istasyonuna konum, yükseklik, sıcaklık, nem bilgilerini anlık olarak iletmektedir. Roketimizin birbirinden ayrı iniş yapan bütün parçalarında GPS ve telemetri sistemi bulunmaktadır. Gövde üretimi için İskenderun Teknik Üniversitesi Makine Mühendisliği Bölümü mekanik laboratuvarı kompozit atölyesinde vakum infüzyon yöntemi ile silindirik kesite sahip kompozit parça üretim denemesi yapılmıştır. Kanatçık geometrisi olarak Openrocket simülasyonları sonucunda delta tipi kanatçık uygun görülmüştür. Ayrıca tasarımı yapılıp üretilmesi planlanan ALP-01 katı yakıtlı roket ile Teknofest 2019 roket yarışmasına katılınması planlanmaktadır. Çalışma aşamalarında, ikisi statik test olmak üzere dört kez katı yakıtlı roket motoru denemesi yapılmıştır. Denemelerde kullanılan yakıt karışımı (KNO3 Sükroz/Dekstroz) Makine Mühendisliği bölümü mekanik laboratuvarı kompozit atölyesinde bulunan hassas terazi, ayarlı ocak, hidrolik pres vb. ekipmanlar kullanılarak hazırlanmıştır., In this study the design of solid-fuel low-altitude rocket ALP-01 CAD has been optimized for the selected engine of rocket sizes for an altitude of 1500 meters. Parabolic type was preferred as the cone geometry. The length is calculated as 35cm. 3D printer for nose cone and shoulder section will be prepared by hand and made from glass fiber by hand method. Two different rescue mechanisms have been used in our rocket. CO2 tube discharge mechanism was used for the removal of the nose cone, payload, payload parachute and the first parachute from the rocket. Payload has a flight computer with a telemetry system. This computer instantly transmits location, altitude, temperature and humidity information to the ground station. There are GPS and telemetry systems in all parts of our rocket. The production of composite parts with cylindrical cross-section was performed and positive results were obtained in the composite workshop of the Mechanical Engineering Laboratory of Iskenderun Technical University. As a result of Openrocket simulations as a wing geometry, delta-type flaps were considered suitable. Furthermore, it is planned to participate in Teknofest 2019 rocket competition with ALP-01 solid fuel rocket which is planned to be designed and produced. Four times solid-fuel rocket engine trials, two of which were static tests, were conducted in the study stages. The fuel mixture used in the experiments (KNO3Sukroz / Dextrose) is located in the Mechanical Engineering Laboratory of Iskenderun Technical University.

Purpose The purpose of this paper is to investigate the effect of doping element on the microwave absorption performance of hexagonal nano boron nitride (h-nBN)-reinforced basalt fabric (BF)/epoxy composites. A new type of hybrid composite that will be produced by the use of boron nitride as an additive that leads to increased radar absorption capability will be developed and a new material that can be used in aeronautical radar applications. Design/methodology/approach This study is focused on the microwave absorption properties of h-nBN doped basalt fabric-reinforced epoxy composites. Basalt fabric (BF)/epoxy composites (pure composites) and the BF/h-nBN (1 Wt.% h-nBN doped composites) hybrid composites were fabricated by vacuum infusion method. Phase identification of the composites were performed using X-ray diffraction (XRD), the 2θ scan range was from 10 to 60 with the scanning speed of 3°/min and surface morphologies of the composites were investigated using scanning electron microscopy (SEM). Microwave properties of samples were investigated through transmission/reflection measurements in Agilent brand 2-Port PNA-L Network Analyzer in the frequency range of 3–18 GHz. The prepared sample is positioned between two horn antennas with and without metal plate. Findings Experimental results show that h-nBN doped composite was synthesized successfully and the produced hexagonal nano boron nitride-added fiber laminated composite material has good absorption behavior when they are used with metallic sheets and good for isolation applications at many points in the 3–18 GHz band. Originality/value This paper will contribute to the literature on the use of basalt fabric, which are new types of fibers, and hexagonal nano boron nitride and the effects of boron nitride on radar absorption properties of composite material. It presents detail characterization of each composite by using XRD and scanning electron microscopy.

The aim of this work is to investigate the effect of the hexagonal nano boron nitride (h-BN) doped epoxy on the mechanical performances and machinability behaviors of basalt fiber (BF) composites. The h-BN has used as a dopant with a weight rate of 1 wt. %. The polymer composites were prepared by the vacuum bagging method and specimens were processed with abrasive water jet machining (AWJM) to analyze the machinability of the material. A circular hole with an 8 mm size was machined by abrasive water jet (AWJ) on the composite plate with a thickness of 2.3 ± 0.1 mm using the garnet size of 80 µm as an abrasive. Taper angle and circularity of machined hole, the entry-exit hole diameter, delamination, splintering, burring, thickness, and hardness were measured. Results indicate that cutting speed has a high influence on the taper angle and circularity respectively.

WOS: 000510107300008, In this study, cutting of multi-walled carbon nanotubes (MWCNTs)-doped composite sheets by abrasive water jet machining (AWJM) and the effects of the water jet on cut composite materials were analyzed. The influence of MWCNTs doping to glass fiber-reinforced polymer composite plates was investigated. In addition, mechanical properties of doped composite and the effects of cutting by AWJM method were determined. It has been found that the addition of nanoparticles to layered glass fiber composite materials plays an effective role in the strength of the material and affects the abrasive water jet (AWJ) cutting quality. Additionally, composite materials were drilled using different water jet cutting parameters such as cutting speed, fixed nozzle diameter, cutting pressure and abrasive garnet. The entry-exit hole diameter, kerf, delamination, splintering, burring, thickness and hardness change were investigated. As the cutting speed increased, rotational slip, cutting start point, circularity and circular error increased. The thickness of the composites cut by water jet method increased and surface hardness decreased due to delamination. As the cutting speed increased, the hole inlet and outlet dimensions increased, which leads to an increased in size of the kerf.

In this study, the effects of low amount (0.1 wt%) multi-walled carbon nanotube (MWCNTs) distributed homogenously in epoxy via cationic surfactant (cetyl pyridiniumchloride-CPC), polyacrylonitrile nanofiber (in the range of 240–570 nm diameter) mats between each lamina, main fiber-matrix interface improvement using γ-Glycidoxypropyltrimethoxysilane and intermediate combinations were investigated on the fracture toughness of E-Glass/epoxy laminate. Considering the data obtained from three-point bending test samples with a single edge crack, it was found that the ultimate bending strength, modulus and fracture toughness of the silane-treated samples increased by 25.6%, 4.9 and 16.6% respectively, with respect to the reference sample. When MWCNTs was added to the silane treated sample, it was observed that it did not enhance the fracture toughness and decreased the strength and modulus slightly (1%) with the effect of CPC. The effect of 128 μm thick nanofiber mats on the silane-treated sample did not occur as expected and was found to cause delamination by working as a separate layer between the laminae.

PurposeThe purpose of this paper is to investigate cotton fabric behavior that is exposed to radar waves between selected operation frequencies as an alternative radar-absorbing material (RAM) response. Cotton fabric biocomposite materials were compared with carbon fabric composite materials, which are good absorbers, in terms of mechanical and electromagnetic (EM) properties for that purpose.Design/methodology/approachThe laminated composite plates were manufactured by using a vacuum infusion process. The EM tests were experimentally performed with a vector network analyzer to measure reflection, transmission and absorption ability of cotton fabric, carbon fabric and cotton–carbon fabric (side by side) composite plates between 3 and 18 GHz. The tensile and low-velocity impact tests were carried out to compare the mechanical properties of cotton fabric and carbon fabric composite plates. A scanning electron microscope was used for viewing the topographical features of fracture surfaces.FindingsThe cotton fabric composite plate exhibits low mechanical values, but it gives higher EM wave absorption values than the carbon fabric composite plate in certain frequency ranges. Comparing the EM absorption properties of the combination of cotton and carbon composites with those of the carbon composite alone, it appears that the cotton–carbon combination can be considered as a better absorber than the carbon composite in a frequency range from 12 to 18 GHz at Ku band.Originality/valueThis paper shows how cotton, which is a natural and easily supplied low-cost raw material, can be evaluated as a RAM.

When designing unmanned aerial vehicles (UAVs), it istaken into consideration that certain features are met. In some UAVs, modelsare designed according to the maximum speeds that can be reached, while inothers, they are designed according to the maximum lifting forces. In thisstudy, flight parameters were calculated by aerodynamic analysis performed inan analysis program in order to reach the maximum range of a designed UAV andthen the UAV was produced. During the aerodynamic analysis, first the wing profileand then the whole body were analyzed. As a result of the analyzes, the mostsuitable angle of attack for minimum power requirement and maximum range wasobtained as 12° and 8°, respectively., İnsansız hava araçları tasarlanırken birtakım özelliklerin karşılanması göz önünde bulundurulur. Bazı insansız havaaraçlarında ulaşılabilecek maksimum hızlara göre modeller tasarlanırkenbazılarında ise maksimum taşıma kuvvetlerinin oluşması istenebilir. Buçalışmada tasarımı yapılmış bir insansız hava aracının maksimum menzileulaşabilmesi için uçuş parametreleri bir analiz programında yapılan aerodinamikanaliz yardımı ile hesaplanmış ve ardından İHA’nın üretimi yapılmıştır.Aerodinamik analizler yapılırken öncelikle kanat profilinin daha sonra tümgövdenin analizi yapılmıştır.

WOS: 000469772600019, AISI D2 steel is the most commonly used cold-work tool steel in its grade. In this study, microstructural characterization and some mechanical properties of borided AISI D2 steel samples were investigated. The boriding treatment was carried out at 900 and 1000 degrees C for 3, 5 and 7 hours by using Ekabor 2 powder and a solid-state box boriding technique. Wear behavior of borided and non-borided steel were conducted by linear reciprocating wear test using an Al2O3 ball as the counterpart. The sliding distances and the sliding speed were remained constant at 250 m and 5 mm/s, respectively, with the loads of 10, 20 and 30 N (being applied). Microstructural characterization revealed homogeneous, dense and fine-grained structure which had predominant dual phase boride (FeB+Fe2B) layer with minor of Cr-B, Mo-B, V-B, Mn-B interstitial compounds being present as well. The thickness and hardness values of the boride layer were in the range of 46.23-126.8 mu m and 2005-2227 HV0.1, respectively, depending on the process conditions. The results showed that the wear resistance improved by up to 6.7 times in comparison with non-borided AISI D2 steel. Severe plastic deformation was the effective wear mechanism in non-borided AISI D2 steel. However for the samples which were borided at 900 and 1000 degrees C, delamination and polishing type of wear mechanisms were observed, respectively. Surface hardness and boride layer thickness had a great effect both on wear rate and wear mechanism.

The effect of various amounts (1, 2, and 4 wt%) of hexagonal nano boron nitride on the mechanical properties of carbon/basalt fabric reinforced epoxy hybrid composite laminates has been investigated through experimental methods. The hybrid composites were fabricated using hand lay-up and vacuum infusion techniques. The produced hybrid nanocomposites were characterized by SEM-EDS Mapping, XRD, and FT-IR analyses. In order to find the strength of the composites under the influence of uniaxial tensile, tensile experiments were conducted in ASTM D3039 standard, bending experiments in ASTM 7264, and impact experiments in ASTM D256 standard. The fracture morphologies were investigated after the tensile test using a stereomicroscope. The results of this study showed that the mechanical properties of hybrid composites were substantially improved by the addition of h-nBNs fillers at 1 wt% because of the high adhesion strength in the interphase between h-nBNs epoxy-fiber interactions.

WOS: 000372851000015, This paper describes the fatigue failure of a rotary dryer in a chemical plant. The process conditions required the dryer to be rotated continuously at a speed of about two and half revolutions per minute. The shell structure of this large drum is formed by combining segmented shell parts using bolted ring flange joints. Because of the gross weight of the dryer in operation time, each joint was subjected to bending moment. In the first two years in service, micro cracks were occurred by fatigue. The failure was analyzed using the fatigue curves given in ASME Boiler and Pressure Vessel Code Section VIII Division 2 and EN 13445 Unfired Pressure Vessels Part 3 Codes. Finally, flange joints were removed from the drum and new cylindrical parts adapted to the drum using butt welding after reaching better results in FEM and fatigue calculation. (C) 2016 Elsevier Ltd. All rights reserved.

The Surface Response to Excitation (SuRE) method excites the surface of the structure with a piezoelectric element. The generated vibrations at critical points on the surface are measured with other piezoelectric elements, a laser vibrometer or other sensors. Then the magnitude of the transfer function between the excitation and the sensory signal is monitored. The performance of the SuRE method was evaluated using a low cost Digital Signal Processor (DSP) system, spectrum analyzer, and laser vibrometer. The accuracies of the Teager–Kaiser (TKA), Goertzel, RMS and average of the positive values algorithms were evaluated for magnitude estimation. The SuRE method was employed successfully for detection of compression loads by using the DSP system. Existence of composite coating was inspected using a spectrum analyzer. Finally, the method was used to detect localized loads on an aluminum plate with a laser vibrometer. The study indicated that the SuRE method may be used as a low cost alternative to impedance method. The inconvenience of using separate sensor(s) is the disadvantages of the SuRE method respect to the impedance method. The main advantages are requirement of simpler and cheaper instrumentation for data analysis, defect location estimation capability when multiple sensors are used, faster data acquisition at low noise environments, and allowing non-contact sensors such as laser vibrometers for measurement of surface response.

The performances of completed manufacturing processes were evaluated using the surface response to excitation (SuRE) and Lamb wave methods. Both methods used the same piezoelectric elements attached to the surface of the workpiece. The SuRE method and the Lamb wave method were used to identify the structural changes created by welding, drilling, coating, filling a slot with glue, and composite patching. This study indicates that the tested methods are feasible for part based process performance monitoring (PbPPM) which evaluates the quality of the completed process with the sensors attached to the workpiece.

WOS: 000381839900017, This paper describes the fatigue failure of girth gear manufactured from low alloy cast steel of rotary dryer in a chemical plant. The cracks of T-section web of the girth gear occurred at the end of 25 year working period because of stress intensity factor. Because of normal condition of working surfaces of teeth, spare gear was not thought and repair welding was the only option. Nickel based super alloy electrode was used for repairing and it had been successful until the new gear was ordered. The factors behind the fatigue failure and the reasons of temporary repairment were discussed using the cause-effect diagram. Higher grade bolt using instead of design grade, insufficient stiffener of web, insufficient preparation of repair welding and wide section welding beads at the welding deposits were found as the reasons of changing the girth, gear with the new one. (C) 2016 Elsevier Ltd. All rights reserved.

Piezoelectric materials generate electricity when they are subjected to dynamic strain. In this paper compact size self contained energy harvesters were built by considering typical space available for AA size batteries. Each of the harvesters contains a rectifier circuit with four diodes and a capacitor. A series of piezoelectric energy harvesters with circular and square cross-sections were built and tested at different frequency and amplitude levels. On 1M? impedance digital oscilloscope, it was observed that the voltages reached to 16V (round cross-section) and 25V (square cross-section) at 50Hz frequency. The highest power output accomplished was 625µW. The outputs of both types of the harvesters were very similar at low amplitudes. However, the square cross-section facilitates better attachment of the piezoelectric elements with the harvester shell and worked efficiently at higher amplitudes without immediate failure.

In this study mechanical and thermal properties of epoxy resin reinforced withdifferent numbers of nanofiber layers which produced with electrospinning method wasinvestigated. Solution of 10 wt% of polyacrylonitrile (PAN) in N,N-dimethylformamide(DMF) was used for electrospinning. The diameters of the obtained nanofibers were in therange of 380-420 nm. The average thickness of the produced nanofiber layer was about200 ?m. The special molds were prepared to produce the laminated composite plates. Thetensile tests show that the using of nanofiber PAN layers increase the tensile force 34.54%and decrease the elongation 8.87% in comparison with neat epoxy. The fracture surfaces ofthe specimens were inspected by using optical and scanning electron microscopy (SEM).The thermal properties of the nanofiber layered composites were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. It wasobserved that the glass transition temperature increased parallel to this as the number ofPAN layers increased and rose up to 86?C, while the thermal stability did not show mucheffect of PAN layers., Bu çalışmada elektrospin metodu ile üretilmiş farklı sayılardaki nanofiber takviyelitabakalı epoksi kompozitlerin mekanik ve termal özellikleri araştırılmıştır. Elektrospinişlemi için ağırlıkça %10 oranında poliakrilonitril (PAN) ve N,N dimetilformamid (DMF)çözeltisi kullanılmıştır. Elde edilen nanofiber çapları 380-420 nm aralığındadır. Üretilennanofiber tabaka kalınlığı ortalama 200 ?m’dir. Tabakalı kompozit plakaları elde etmekiçin özel kalıplar hazırlanmıştır. Çekme deney sonuçları nanofiber tabaka kullanımınınçekme kuvvetini saf epoksiye oranla % 34.54 arttırdığı ancak uzamayı saf epoksiye oranla% 8.87 azalttığı belirlenmiştir. Numunelerin kırılma yüzeyleri optik ve taramalı elektronmikroskopu (SEM) ile incelenmiştir. Üretilen nanofiber tabakalı kompozitlerin termalözellikleri termal gravimetrik analiz (TGA) ve diferansiyel taramalı kalorimetre (DSC)analizleri ile belirlenmiştir. Camsı geçiş sıcaklığının PAN tabaka sayısı arttıkça buna paralelolarak arttığı ve 86 C ye kadar çıktığı, termal kararlılıkta ise PAN tabakalarının etkisininçok fazla olmadığı görülmüştür.

The postimpact buck ling loads of E-glass/epoxy laminates have been measured. Composite samples with the stacking sequence [+45/−45/90/0]2s were subjected to low-speed impact loadings at various energy levels. The tests were conducted on a specially developed vertical drop-weight testing machine. The main impact parameters, such as the peak load, absorbed energy, deflection at the peak load, and damage area, were evaluated and com pared. The damaged specimens were subjected to compressive axial forces, and their buckling loads were determined. The relation between the level of impact energy and buck ling loads is investigated.

The work described herein consists of experimental measurement of the post-impact buckling loads of E- glass/epoxy laminates. Composite samples with stacking sequence of [+45/?45/90/0]2s were subjected to low-velocity impact loading at energy levels of 36, 56.13, 79.95, 110.31 and 144 J. The impact tests were conducted with a specially developed vertical drop weight testing machine. Impact parameters like peak load, absorbed energy, deflection at peak load and damage area were evaluated and compared. Damaged specimens were subjected to compressive axial forces and buckling loads of the specimens were obtained. The relation between energy levels and buckling loads is investigated.

In this study, mechanical buckling behaviors of composite square plates of four symmetric and antisymmetric layers with holes are examined. A thermoplastic material is used as the matrix material. Two different reinforced materials are used, of which one is a galvanized steel wire and the other a woven galvanized wire. The hole type is taken as circular. The finite element method is used for the solution. First critical buckling loads of an orthotropic plate with and without hole subjected to unidirectional compression are found. The results are illustrated in figures.

An elastic-plastic stress analysis and the expansion of plastic zone in layers of woven steel fiber-reinforced thermoplastic matrix-laminated plates are studied by using the Finite Element Method and the First-order shear deformation theory for small deformations. Composite structures consisting of woven Cr-Ni wire as a fiber and F2.12 low-density polyethylene as a thermoplastic matrix were manufactured by hot-press molding. The mechanical properties were experimentally determined. The effect of orientation angle and symmetric-antisymmetric structures were investigated. It is assumed that the laminated plates are subjected to in-plane uniform loads. Loading is gradually increased from yield point of the plate as 0.01 MPa at each load step. Load steps are chosen as 300, 400, and 500.

In this study, fatigue behavior of filament wound composite pipes under alternating internal pressure has been investigated. GRP pipes which made of E-glass/epoxy are tested under open ended conditions. Test specimens have four layers which have ±55° winding angle. Tests have been done in accordance with ASTM D-2992. This standards offers 0.42 Hz frequency and R = 0.05 stress ratio. Tests have been performed at different load levels from 30% to 70% of ultimate strength. Whitening, leakage and final failure levels of GRP pipes have been observed. Fatigue results are presented and interpreted by means of S–N curves.

A thermal buckling analysis of symmetric and antisymmetric angle-ply laminated hybrid composite plates with an inclined crack subjected to a uniform temperature rise is presented in this paper. The first-order shear deformation theory in conjunction with the variational energy method is employed in mathematical formulations. The eight-node Lagrange finite-element technique is used for determining the thermal buckling temperatures of hybrid laminates. The effect of crack size and stacking sequences on the temperatures is investigated.

Thermoplastic matrix reinforced with metal fiber, composite laminated plates were anufactured by using moulds. The symmetric and antisymmetric laminated plates were loaded by in-plane forces. An elastic-plastic numerical solution has been carried out by finite element technique (FEM) for some load steps. Residual stresses and expansion of plastic zone have been illustrated in tables and figures., Metal lif takviyeli termoplastik matrisli tabakalı kompozit plaklar sıcak pres metoduyla imal edilmiştir. Simetrik ve anti-simetrik tabakalı kompozit plaklar kendi düzlemine paralel yüklere maruzdur. Elastik-plastik sayısal çözüm bazı yük adımları için sonlu elemanlar yöntemiyle (SEM) gerçekleştirilmiştir. Plaklardaki artık gerilmeler ve plastik bölgeler tablolar halinde verilmiş ve şekillerle gösterilmiştir.

In the simulation programs that used to estimate the power of the organic Rankine cycle; high error rates may have occurred due to accepting ideal or near-ideal behaviour differ from the actual behaviour of system components. Predictions made via artificial neural networks may be more close to actual results in the system which is of non-linear behaviour. In this study, network was trained by evaporator waste heat input- output temperatures and mass flow rate, cooling fluid input- output temperatures and mass flow rate taken from an experimental organic Rankine cycle. The power prediction was made with trained network and then the experimental and prediction results of the 10 kW organic Rankine cycle was compared. At the end of the study, the values obtained from artificial neural network were compared with experimental data and correlation coefficient which shows performance of network has calculated to be 0.99124. The prediction success of network was also checked via performing different test data input to the network.

Performance of the Surface Response to Excitation (SuRE) method was evaluated by using a low cost DSP system and spectrum analyzer. SuRE method excites the surface of the structure with a piezoelectric element. The generated vibrations of a critical point on the surface are measured with (a) piezoelectric element(s) or other sensor(s). The magnitude of the transfer function between the excitation and the sensory signal is monitored. The accuracies of the Teager-Kaiser (TKA), Goertzel, RMS and average of the positive values algorithms were evaluated for magnitude estimation. The SuRE method was used successfully for detection of the compression by using the DSP system. In addition, an applied compressive force, a change of the diameter of a hole and a composite coating was detected by using a spectrum analyzer. The study indicated that the SuRE may be used as a low cost alternative to impedance method. The cost and inconvenience of using multiple piezoelectric elements are the disadvantageous of the method. The main advantages of the SuRE are requirement of much cheaper and simpler equipment. Test time may be drastically shortened in low noise environments, many different transducers may be used for sensing and some directionality may be gained by carefully selecting the location of the sensor(s).

Lamb wave method detects the defects from the propagation characteristics of the created brief harmonic signals. Generally, the defects are detected by analyzing the delays and amplitudes of the received waves. The envelopes of the sensory signals may be used to calculate the delays and amplitudes of the received signals. Sometimes, similar envelopes could be observed at different test conditions. Use of the time-frequency spectra of the s-transformation is proposed for distinction of the problems when the envelopes of the monitored signals are very similar. In the study, a beam was compressed from different points with a hydraulic crimping tool. In separate tests, the cross sectional area at the middle of the beam was reduced by opening slots. The envelopes and time-frequency spectra of the sensory signals were calculated by using the s-transformation. The difference of the time-frequency spectra successfully distinguished the test condition when the envelopes were very similar.