This study compared the characteristic properties of the yarns produced on three different yarn spinning systems with the same material. These spinning systems are conventional ring, compact, and compact-jet. Compact-jet is a proper combination of compact and jetring-spinning systems and therefore it is less known. On the other hand, conventional ring and compact spinning systems are well known in the spinning field. When the compact-jet spinning system was designed, it was aimed to gather the advantages of the jetring and compact spinning systems. Therefore, an air nozzle was placed between the exit of the RoCoS compact unit and the yarn guide of the spinning system. At the end of the study, it was determined that the compact-jet yarn properties are different from that of the conventional ring and compact yarns. The compact-jet spinning system is mainly effective on yarn hairiness and compact-jet yarn is superior compared with other yarns.

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Hairiness affects the post-spinning processes and fabric appearance. In order to reduce the yarn hairiness, the present work attempted to design and develop an air nozzle that can be easily attached on to the sirospun spinning system. The system, based on a nozzle attachment to the sirospun spinning system, is named the siro-jet. In our previous studies, the nozzle was used in ring and compact spinning processes and the changes in yarn properties were analyzed. In this study, various nozzles having different injector angles, main hole diameters, injector diameters, number of injectors, nozzle shapes and injector positions were used and siro-jet yarns were produced at different air pressure levels. At the end of the experiments, it was determined that there is an optimum value for each nozzle parameter, and that the number of injectors and injector position play the most important roles in reducing yarn hairiness, whereas nozzle shape shows the weakest effect. On the other hand, the findings showed that it is possible to get lower hairiness values by different modifications on the same nozzle design. Considering the hairiness results, a constant was defined indicating the relationship between nozzle structural parameters and hairiness of the yarns to ease the nozzle design efforts. Depending on nozzle type, the siro-jet spinning system truly improves the yarn hairiness by 40-75%. In the literature, many researchers used an air nozzle in the spinning and also the winding processes. However, the combination of the air nozzle and sirospun spinning system in this manner is still not a common application.

Jetring is a modifi cation of the conventional ring spinning system and based on the usage of an air nozzle and pressurized air during yarn spinning. This study researched the characteristic properties of Jetring yarns and compared Jetring and conventional ring spun yarn properties. For the Jetring yarn production, three different nozzle types having different injector angles and four different air pressure levels were used. In addition to 30 ° and 45 ° injector angles, which are widely reported in literature, the effect of an angle of 15 ° was also studied. At the end of the study, the differences between Jetring and ring spun yarns were determined. It was found that the Jetring spinning system produces yarns having a hybrid character between conventional ring and air-jet yarns. Additionally, the yarn properties of Jetring yarns highly depend on nozzle structural parameters and air pressure level.

Hairiness significantly influences the appearance of yarns and fabrics. New methods and spinning systems have been offered to reduce it. Nevertheless, there is still the quest for easy, low-cost processes to produce good quality yarns with reduced hairiness. Therefore, due to its considerable importance for spun yarns, we worked on a new spinning method to decrease yarn hairiness. Many researchers have been studying the use of air nozzles in the spinning and also the winding processes, and they indicated that hairiness decreases by up to 40-50%. From this point, we investigated the use of an air nozzle on a compact spinning system and discussed the effect on yarn hairiness. The nozzle was positioned at the exit of the drafting system on a RoCoS compact spinning system and pressurized air was fed into the nozzle by the compressor during spinning. We called the combination of an air nozzle and a compact spinning system a Compact-Jet spinning system. In the literature, there are no such trials. At the end of the study, it was determined that a Compact-Jet spinning system truly improves hairiness by up to 40% in comparison to the compact spinning system and by up to 70% compared with the conventional ring spinning system. Regarding the nozzle structural parameters, the changes in hairiness indicate that the main hole diameter and nozzle outlet design make the most important contributions in reducing yarn hairiness; whereas the injector angle and nozzle head type show weaker effects. As a result, the Compact-Jet can be considered as an innovative spinning system providing the opportunity to produce less hairy yarn. Additionally, we believe that this study makes an important contribution to the research activities in the spinning field and its associated literature.

No abstract

In this study, behavior of a viscoelastic material under external loading has been systematically investigated in the frame of continuum mechanics, where the material was brought to a composite state by two independent and non-expansive fiber families. The matrix material is supposed to be made of viscoelastic material involving an artificial anisotropy due to fiber reinforcing by arbitrary distribution. In terms of behavior the object responds to the environment prompting it through elastic stress and dissipative stress, whose constitutive equations have been obtained. While elastic stress is derived from the thermodynamic potential, dissipative stress was formed as a tensorial function that depends on certain arguments. These arguments are Green deformation tensor, deformation rate tensor, fiber distribution tensor and temperature field. As a result, constitutive equations obtained were used as substitutes in balance equations, yielding field equations.

Bu çalışmada, titanyum karbür (TiC) ile güçlendirilmiş ağırlıkça katkısız, %1, %3 ve %5 oranında TiC içeren epoksi reçineli cam/kevlar kumaş hibrit kompozit plakalar hazırlanmıştır. Tüm hazırlanan kompozit panellerin deneysel ve sayısal olarak mekanik özellikleri ve darbe davranış ölçümleri incelenmiştir. Kompozit plakalar elle yatırma yöntemi ile hazırlanmıştır. 207gr/m 2 yüzey alanına sahip düz aramid fiber (Kevlar 49), 300gr/m 2 yüzey alanına sahip cam fiber ve F-1564 epoksi reçineler sırası ile takviye edici ve matris malzeme olarak kullanılmıştır.Kompozit panellerin mekanik özelliklerini belirlemek için elastisite modülü, kayma modülü ve poision oranı universal çekme test cihazı ile elde edilmiştir. Kompozit paneller 100x100 mm boyutlarında kesilmiştir. 12 tabakalı plakaya sahip numuneler 3 sıra kevlar 1 sıra cam elyaf tabaka olmak üzere sıralanmıştır. ANSYS dinamik analiz programı ile elde edilen ölçüm verileri sayısal olarak kıyaslanmıştır.Sonuç olarak, 10J, 20J ve 30J darbe enerjileri altında elde edilen kuvvet-çökme, kuvvet-zaman, absorbe edilen enerji-zaman ve hız-zaman grafikleri darbe testinde elde edilmiştir. Farklı konsantrasyonlar oranlarında eklenen TiC takviyeli hibrit kompozit plakalara yapılan mekanik ve darbe testleri sonucunda %3 ağırlıkça TiC takviye edilmiş kompozit plakalarda saf kompozit plakaya nazaran elastisite modülünde %15 oranında iyileşme ve darbe direncinde %6 oranında daha fazla enerji absorplandığı görülmüştür. Fiber dağılımları ve kırılması uygulanan yükler altında tüm numunelerde görülürken herhangi bir delinme olayı kompozit panellerin alt yüzeyinde görülmemiştir. Sayısal analizlerle elde edilen sonuçlar ise deneysel sonuçları arasında uyumlu bir ilişki görülmüştür.