Publication: Karbon lif ve mineral katkılı akıllı harçların mekanik ve yüksek sıcaklık performansının araştırılması
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Authors
Çağlayan, Alim Berk
Advisor
Öztürk, Murat
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Bursa Uludağ Üniversitesi
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Abstract
Bu çalışmada, kesikli karbon liflerle takviye edilmiş çimentolu harçların mekanik performansı, yüksek sıcaklık dayanımı, kuruma büzülmesi davranışları ve kendini algılama özellikleri incelenmiştir. Çalışmada, farklı lif boyları ve içerikleri ile mineral katkılar (silis dumanı, uçucu kül, yüksek fırın cürufu) kullanılarak üç grup numune hazırlanmış ve bu değişkenlerin malzeme özelliklerine etkileri değerlendirilmiştir. Kesikli karbon liflerin çimentolu kompozitlerin eğilme ve basınç dayanımını artırdığı ve farklı lif boylarının birlikte kullanımının çatlak oluşumunu sınırlandırarak daha yüksek dayanımlar sağladığı belirlenmiştir. Mineral katkılar, mekanik performansı iyileştirirken, yüksek sıcaklık dayanımı üzerinde de önemli etkiler göstermiştir. Özellikle, silis dumanı ve yüksek fırın cürufu içeren numuneler yüksek sıcaklık sonrası daha iyi performans sergilemiştir. Ayrıca lif varlığının, yüksek sıcaklık sonrasında gelişen mekanik dayanımlardaki azalmaları sınırlandırdığı belirlenmiştir. Büzülme davranışlarında, farklı boylardaki karbon liflerin birlikte kullanımının malzemenin hacim stabilitesini artırdığı gözlenmiştir. Basınç yüklemesi esnasında gerilme algılaması uygulamalarında ise karbon liflerin malzemeye kazandırdığı piezo-resistif özellikler sayesinde elektriksel iletkenlikteki değişimlerin mekanik hallerle ilişkilendirilebileceği belirlenmiştir. Ancak, liflerin homojen dağılımındaki yetersizlik, iletkenlik sürekliliğinin sağlanamaması ve malzeme içindeki porozite gibi faktörler, kendini algılama performansını sınırlamıştır. Sonuç olarak, bu tez, kesikli karbon lif katkılı çimentolu kompozitlerin mekanik, termal ve elektriksel özelliklerini geniş bir perspektiften değerlendirerek çok fonksiyonlu akıllı ve yenilikçi malzemelerin geliştirilmesine yönelik önemli bilgiler sunmaktadır.
In this study, the mechanical performance, high-temperature resistance, drying shrinkage behavior, and self-sensing properties of cementitious mortars reinforced with discontinuous carbon fibers were investigated. Three groups of samples were prepared using different fiber lengths, fiber contents, and mineral admixtures (silica fume, fly ash, and ground granulated blast-furnace slag), and the effects of these variables on the material properties were evaluated. It was found that discontinuous carbon fibers enhanced the flexural and compressive strength of cementitious composites, and the combined use of fibers with different lengths effectively limited crack formation, resulting in higher strength levels. While mineral admixtures improved mechanical performance, they also significantly influenced high-temperature resistance. Notably, specimens containing silica fume and ground granulated blast-furnace slag demonstrated better performance after exposure to high temperatures. Additionally, the presence of fibers was observed to mitigate the reductions in mechanical strength caused by high-temperature exposure. In terms of shrinkage behavior, the combined use of carbon fibers with different lengths was found to improve the volumetric stability of the material. For self-sensing applications under compressive loading, the piezo-resistive properties imparted by carbon fibers allowed changes in electrical conductivity to be correlated with mechanical states. However, limitations such as insufficient homogeneous distribution of fibers, the lack of conductivity continuity, and the porosity within the material restricted the self-sensing performance. In conclusion, this thesis provides valuable insights into the mechanical, thermal, and electrical properties of discontinuous carbon fiber-reinforced cementitious composites, offering a comprehensive evaluation for the development of multifunctional, intelligent, and innovative materials.
In this study, the mechanical performance, high-temperature resistance, drying shrinkage behavior, and self-sensing properties of cementitious mortars reinforced with discontinuous carbon fibers were investigated. Three groups of samples were prepared using different fiber lengths, fiber contents, and mineral admixtures (silica fume, fly ash, and ground granulated blast-furnace slag), and the effects of these variables on the material properties were evaluated. It was found that discontinuous carbon fibers enhanced the flexural and compressive strength of cementitious composites, and the combined use of fibers with different lengths effectively limited crack formation, resulting in higher strength levels. While mineral admixtures improved mechanical performance, they also significantly influenced high-temperature resistance. Notably, specimens containing silica fume and ground granulated blast-furnace slag demonstrated better performance after exposure to high temperatures. Additionally, the presence of fibers was observed to mitigate the reductions in mechanical strength caused by high-temperature exposure. In terms of shrinkage behavior, the combined use of carbon fibers with different lengths was found to improve the volumetric stability of the material. For self-sensing applications under compressive loading, the piezo-resistive properties imparted by carbon fibers allowed changes in electrical conductivity to be correlated with mechanical states. However, limitations such as insufficient homogeneous distribution of fibers, the lack of conductivity continuity, and the porosity within the material restricted the self-sensing performance. In conclusion, this thesis provides valuable insights into the mechanical, thermal, and electrical properties of discontinuous carbon fiber-reinforced cementitious composites, offering a comprehensive evaluation for the development of multifunctional, intelligent, and innovative materials.
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Keywords
Karbon lif, Çimento, Harç, Kendini algılama, Büzülme, Mekanik dayanımlar, Carbon fiber, Cement, Mortar, Self-sensing, Shrinkage, Mechanical strength