Faculty Publications
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Item Experimental investigation on Mode-I fracture toughness of Carbon-Carbon composites fabricated by preformed yarn method(Elsevier Ltd, 2021) Sunil Kumar, B.V.S.; Neelakantha Londe, V.; Lokesha, M.; Anilas, M.; Surendranathan, A.O.Carbon-Carbon composites are one such material that gives designers significant importance for advanced applications over conventional materials. They are applied in applications at very high temperatures (up to 3000°C), and under extreme conditions. They have a density which is much less than metals and ceramics and thus, make low part weight a significant factor for aerospace applications. Fracturing toughness is a measurable way to express a substance's resistance to fracture in the case of a break. This paper describes the experimental studies done to investigate the Mode-1 fracture toughness of carbon-carbon composites which was fabricated via the preformed yarn method. Fracture toughness was determined for four different (a/w) ratios i.e. 0.45, 0.47, 0.50 and 0.52 respectively. The results showed that with only two cycles of pitch impregnation, HIP and graphitizing, carbon-carbon composites were successfully produced. The specimen having an (a/w) ratio of 0.45 had a higher fracture toughness value in comparison with all values. As the (a/w) ratio was increasing, the fracture toughness value decreased and the fractured surface clearly shows a brittle fracture behavior. © 2021 Elsevier Ltd. All rights reserved.Item Study on fracture toughness of carbon-carbon composites at low temperatures(Elsevier Ltd, 2022) Sunil Kumar, B.V.S.; Neelakantha, N.V.; Kumar, M.; Lokesha, M.; Vasantha Kumar, S.N.; Surendranathan, A.O.Carbon-carbon composites (C-CC), employed as composites in space and other industries for their outstanding properties. In extreme temperatures, the C-CC has proved to be the most efficient material. C-CC is one of the top thermal quality high-temperature materials such as high-temperature stability, excellent thermal conductivity, and low-temperature expansion coefficients. C-CC brake disks are highly demanded in aviation, trains, trucks, even race vehicles. Although C-CC is normally utilized at very high service temperatures, recently it has been necessary to explore these in low-temperature circumstances as components must also pass through low-temperature conditions in modern applications. In developing engineering structures, materials and systems for their technical safety, durability, and reliability, fractures and damage prevention and evaluation have an important role to play. Fracture toughness means quantifying the resistance of the fracture when a crack occurs. The present experimental study explores the influence of low temperature on the fracture toughness of C-CC. The low temperatures test of the samples has been done at a temperature between -10 °C and -40 °C. The results demonstrate that the fracture toughness value consistently raised as the temperature dropped. The Fluctuation began at a -10 °C from 2 % with a forecast of -40 °C to 32 %. © 2022 Elsevier Ltd. All rights reserved.Item Influence of Precracking Techniques on Fracture Toughness of Carbon-Carbon Composites(Penerbit UTHM, 2021) Sunil Kumar, B.V.S.; Neelakantha, N.V.; Lokesha, M.; Surendranathan, A.O.Abstract: Carbon-Carbon composites are one such material which give designers significant importance for advanced applications over conventional materials. The remarkable characteristics of carbon-carbon composites had made these products initially extremely useful in the field of aerospace and defense applications. Now, they are presently used in many applications such as biomedical implants, glass, and high temperature glass, etc. In material science, fracture toughness is a trait that depicts the ability of a material to withstand fractures and is one of the most important features in many design applications of any material. A precracked specimen is a sample that is used to accurately assess the distribution of cracks and it is a favored method. This paper describes a comparison of four precracking techniques for carbon-carbon composites using SENB specimen. The potential implications of these techniques on fracture toughness values have been evaluated. The outcome of this work indicates that precracking with a jewel saw is recommended over the other techniques. © 2021. UTHM Publisher. All rights reserved.Item Influence of oxidation on fracture toughness of carbon-carbon composites for high-temperature applications(Gruppo Italiano Frattura, 2021) Sunil Kumar, B.V.S.; Londe, V.N.; Lokesha, M.; Vasantha Kumar, S.N.; Surendranathan, A.O.Carbon-Carbon Composites (C-CC), used as composites for their remarkable qualities in the space industry and in many other industry sectors. C-CC has proven to be the most efficient material in extreme temperature situations. They are one among the best high-temperature materials with good thermal quality, such as high-temperature stability, outstanding thermal conductivity and low-temperature expansion coefficients. In aircraft, railways, trucks and even race vehicles, C-CC brake disks are in high demand. Compared to the favorable thermal and mechanical qualities of C-CC, their great sensitivity to oxidation in an oxidizing environment at temperatures even around 400°C is a major restriction with these composites. In particular, a study of the C-CC oxidation mechanism helps to create protective measures for these composites. The present experimental study explores the influence of oxidation in static air on the fracture toughness of C-CC. At a temperature of around 400°C to 700°C in an increment of 100°C, an oxidation evaluation of the material is carried out. Results show that there was a significant decrease in the fracture toughness when there was an increase in temperature from 400°C to 700°C. We can observe that C-CC fracture toughness is severely affected by oxidation. The decrease in the fracture toughness value in comparison with room temperature was 6% for 400°C and 45% for 700°C. © 2021.