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In this study, the effect of patch sizes and number of patch layers on tensile stress behavior in the repair of elliptical damaged laminated composite sheets was investigated experimentally. For this purpose, glass fiber reinforced laminated composite sheets with elliptical holes were prepared. These plates were subjected to tensile loads and their failure loads were determined experimentally. Then, using DP460 adhesive material, glass fiber reinforced composite sheets with elliptical damage were repaired using single-sided lap joints with glass fiber reinforced composite patches of varying sizes and layer numbers, and the repaired samples were subjected to tensile loads and their failure loads were determined and its effects on stress behavior were also investigated experimentally., Bu çalışmada, eliptik hasarlı tabakalı kompozit levhaların tamirinde yama boyutlarının ve yama tabaka sayısının çekme gerilme davranışına etkisi deneysel olarak araştırılmıştır. Bu amaçla, eliptik delikli cam elyaf takviyeli lamine kompozit levhalar hazırlanmıştır. Bu plakalar çekme yüklerine maruz bırakılmış ve kırılma yükleri deneysel olarak belirlenmiştir. Daha sonra DP460 yapıştırıcı malzeme kullanılarak, eliptik hasarlı cam elyaf takviyeli kompozit levhalar, tek taraflı bindirmeli bağlantıları kullanılarak, değişen boyut ve katman sayılarına sahip cam elyaf takviyeli kompozit yamalarla onarılmış ve onarılan numuneler çekme yüklerine maruz bırakılmış ve kırılma yükleri belirlenmiş ve gerilme davranışı üzerindeki etkileri deneysel olarak araştırılmıştır.

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 study, glass fiber reinforced composite layers which are with and without additives of 0.1 wt.% multi walled carbon nanotubes (MWCNTs) of epoxy were manufactured by vacuum infusion method. Unlike the conventional methods, punching was used in processing and drilling of these materials. The 62 - 64 HRC hard punches made of 1.3343 material with specially designed 90 degrees, 30 degrees, 15 degrees, V, C profiles were used for punching of composites. Additionally, made of 1.2379 material with 62 - 64 HRC hardness, the mold with 0.05, 0.01 and 0.16 mm clearance values was used. Fujifilm prescale and chatillon load cell were used for force measurement that showed the pressure applied by punches with different cutting profiles. Hole diameter, delamination and burring were analyzed by 3d laser scanner. In test values with mold's 0.05 mm clearance, no burr was observed. The cutting surface of MWCNTs doped composite materials was found to be cleaner and material strength was higher.

This paper is focused on the analysis of selected dielectric parameters stability under the conditions of selected accelerated climatic aging. This stability is analyzed for glass fiber reinforced composites with different thermosetting matrix suitable for the production of electrical insulating and also construction elements. Different types of thermosetting resins (epoxy and polyurethane resins) were chosen for the preparation of composites, which are the subject of the presented experiment. Tested composites were firstly characterized in the delivered state and then after the accelerated climatic aging. Important dielectric parameters were evaluated, which are the volume resistivity and the surface resistivity. Two different tests of accelerated climatic aging were realized. The first one was Temperature/humidity cyclic test, which consists of alternated intervals (i) under the temperature of 55 °C and the humidity of 93 %RH and (ii) under the temperature of 25 °C and the humidity of 97.5 %RH. The second one was Damp heat steady state test when samples were exposed to the temperature of 85 °C and the humidity of 85 %RH continuously for 1000 hours. Based on the measured data of resistivities, prospective materials were selected for further activities leading to the production of construction elements with also good electrical insulating properties and with their minimal affection by simulated climatic conditions.

This work describes the composition of the products from solvolysis of thermoset polyester in an acetone/water mixture. A qualitative and quantitative evaluation of the compositions of the aqueous and oil phases was achieved by the combination of liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS/MS), gel permeation chromatography (GPC), and total organic carbon (TOC). Close to 100% of the organic carbon in the aqueous phase was explained by the monomers phthalic acid and dipropylene glycol, co-solvent acetone, and a secondary reaction product, isophorone. In the oil, the most abundant compounds were isophorone, 3,3,6,8-tetramethyl-1-tetralone, and dihydroisophorone. While the first two compounds were intermediates in the self-condensation of acetone, dihydroisophorone has not been reported previously as the by-product of the conventional acetone self-condensation reaction pathway. The quantification results have shown that solvolysis can be successfully used to close the loop in the polymer life cycle while producing a broad spectrum of high-value products that could be recycled for production of polymers, used as a building blocks, or as fine chemicals.

Use of multi-material systems based on fiber-reinforced composites and metal inserts, for instance in many structural components, can lead to numerous technical advantages such as a weight reduction of 40% in the case of vehicles. Known the fiber reinforced composite materials properties, their use in the production process in substitution of metallic materials could be much more rapid knowing the trend of their mechanical properties degradation due to aging caused by environmental conditions even extreme. In this regard accelerated-aging tests may be help to estimate potential long-term serviceability of material systems under expected conditions of use. This paper describeactivities carried out at Materials Technologies Laboratory of ENEA Trisaia Research Centre and results of accelerated aging tests in climatic chambers to characterize carbon and glass fiber reinforced composites for use in automotive sector cith reference to tensile strenght variation. Three climatic zones have been considered for aging tests: temperate, polar, tropical one, each with different values of thermal excursion and relative humidity in order to simulate extreme conditions to which materials may be subjected in their life cycle. The lenght of aging cycles, related to the values of thermal excursions inserted, have reproduced a real-life period of approximately twenty years. The tested samples were characterized by different matrix: polyamide (PA), polyphthalamide (PPA), PA66 nylon, and were reinforcede with class fiber (long and short) and carbon fiber (long and short). All tensile tersts have been performed according to UNI EN ISO 527: 2012 and resukts have been analyzed to identify which FRP had the best performance according to the considered climates Lastly, having a large number of experimental dta resulting from aging test, starting from the fourth step the reaults have been also analyzed using a statistical approach trying to identify a predictive model.

Makina elemanları imalatı, otomotiv yedek parçaları, inşaat, mekanik tesisat ve kimya sektörü gibi pek çok alanda yaygın olarak kullanılan plastiklerin sanayideki kullanım alanları her geçen gün artmaktadır. Yüksek darbe dayanımına ve kimyasal dirence sahip olan plastik malzemelerin cam ve karbon elyafı gibi malzemelerle takviye edilmesi sayesinde mekanik özelliklerinin iyileştirilmesi, plastiklerin kullanım alanlarının ve kullanım oranlarının artışına katkı sağlamaktadır. Plastik enjeksiyon kalıplama plastikler için en yaygın imalat yöntemidir. Enjeksiyon aşamaların herbirinin etkin şekilde uygulanması plastik enjeksiyon kalıplama işleminin veriminin ve elde edilen ürünlerin kalitesinin artırılması açısından son derece önemlidir. Bu çalışmada, otomotiv yan sanayiinde kullanılan bir ara soğutma sistemine ait cam elyaf takviyeli polyamid (PA) 6.6 matrisli bir kazanın plastik enjeksiyon kalıplama ile imalatının simülasyon yolu ile analizi gerçekleştirilmiştir. Bu amaçla öncelikle plastik enjeksiyon kalıplama işlemine ait giriş ve çıkış parametreleri ortaya koyulmuştur. Daha sonra enjeksiyon süresine bağlı olarak enjeksiyon sonrası parçadaki basınç dağılımı, sıcaklık artışı, maksimum kayma gerilmesi bölgeleri ve değeri, kayma oranı, donmuş tabaka oranı, soğuma süresi, çökme izleri, dolum kolaylığı ve çevrim süresinin değişimi sonlu eleman analizleri ile incelenmiştir. Sonuçlar değerlendirilerek uygun enjeksiyon şartları belirlenmiştir. Usage areas of plastics which are commonly used in many industries such as machine component manufacturing, automotive side industry, construction, mechanical installation and chemistry increases day by day. Reinforcement of plastics, which have high impact strength and chemical resistance, with materials like glass and carbon fibers contribute the increase of usage areas and rates of them by improving their mechanical properties. Plastic injection molding is the most common manufacturing method for plastics. Implementing injection stages is extremely important for increasing the efficiency of plastic injection molding process and product quality. In this study, simulation based analysis of manufacturing of an automotive side industry intercooler system boiler made from glass fiber reinforced polyamide (PA) 6.6 with plastic injection molding is realized. For this purpose, input and output parameters of plastic injection molding process are presented at first. Afterwards, variation of pressure distribution, temperature increase, maximum shear stress regions and value, shear rates, frozen layer rates, cooling interval, sink marks, ease of filling and cycle interval depending on injection interval are investigated with finite element analyses. Appropriate injection conditions are determined with the evaluation of results. İÇİNDEKİLER ÖZET -- iv ABSTRACT -- v TEŞEKKÜR -- vi İÇİNDEKİLER -- vii ÇİZELGELER DİZİNİ -- ix ŞEKİLLER DİZİNİ -- x RESİMLER DİZİNİ -- xii SİMGELER VE KISALTMALAR -- xiii 1. GİRİŞ -- 1 2. PLASTİKLER -- 6 2.1. Plastiklerinin Sınıflandırılması -- 6 2.1.1. Termosetler -- 6 2.1.2. Termoplastikler -- 7 2.2. Polyamidler -- 9 2.2.1. PA 6 ve PA 6.6 'nın özellikleri -- 10 2.3. Katkı Maddeleri -- 12 2.3.1. Takviyeli plastikler -- 12 2.3.2. Elyaf takviyeli plastiklerin kullanım alanları -- 13 2.3.3. Plastik takviye malzemesi olarak kullanılan elyaf türleri -- 13 2.3.4. Cam elyaf -- 13 2.4. Plastik Enjeksiyon Kalıplama İşlemi -- 16 2.5. Plastik Enjeksiyon Kalıpları -- 19 2.5.1. Kalıp konstrüksiyonu -- 21 vii 2.5.2. Enjeksiyon kalıplarındaki yolluk sistemleri -- 22 3. AKIŞIN MATEMATİKSEL MODELİ -- 25 4. SONLU ELEMAN ANALİZİ -- 30 4.1. Sonlu Eleman Yöntemi -- 32 4.2. Analiz Prosedürü -- 34 4.2.1. Malzeme -- 34 4.2.2. Eleman boyutunun belirlenmesi -- 35 4.2.3. Yolluk konum ve geometrisinin belirlenmesi -- 37 4.2.4. Kalıp sıcaklığının belirlenmesi -- 40 4.3. Enjeksiyon Analizi -- 41 4.3.1. Enjeksiyon basıncı -- 41 4.3.2. Enjeksiyon sonunda sıcaklık artışı -- 43 4.3.3. Kayma gerilmesi -- 44 4.3.4. Kayma oranı -- 46 4.3.5. Donmuş tabaka oranı -- 47 4.3.6. Soğuma süresi -- 49 4.3.7. Çökme izleri -- 51 4.3.8. Dolum kolaylığı -- 52 4.3.9. Çevrim süresi -- 53 4.4. Enjeksiyon süresi -- 53 5. SONUÇ VE ÖNERİLER -- 56 KAYNAKLAR -- 59 ÖZGEÇMİŞ -- 63