Abstract Natural fiber composites provide an environmentally favorable and sustainable alternative to traditional materials, greatly reducing environmental impact. Aging tests are required to evaluate the long-term mechanical performance and durability of these composites under varied situations, ensuring their dependability and safety over time. This study investigates the effects of ecological aging on jute-banana fiber reinforced phenol-formaldehyde (JBP-F) composites. The experiment involved fabricating JBP-F composites using jute and banana fibers with varying weight ratios (60:40, 50:50, 40:60, 30:70) and subjecting them to various aging tests like long-time water resistance, accelerated water resistance, thermal aging, hydrothermal aging, soil burial test, and accelerated weathering test. The result showed that the composite with a 50:50 jute-banana fiber to resin ratio (JBP-F50) outperformed the other compositions examined in terms of aging resistance. This balanced ratio likely optimized fiber-matrix interaction, leading to superior strength and water resistance. Higher fiber content composites (like JBP-F60) absorbed more water due to weaker bonding, while lower fiber content (JBP-F30) suffered more in high temperatures. All composites experienced strength loss during thermal and hydrothermal aging due to heat and moisture cycles. JBP-F50 again showed the least degradation, possibly due to the resin’s ability to recover. In soil burial tests, biodegradation impacted strength, with higher fiber content composites (JBP-F60) degrading more. Finally, weathering tests revealed some surface deterioration due to UV radiation. However, the resin offered protection, with JBP-F30 (higher resin content) experiencing the most weight loss.JBP-F50, with its balanced fiber-resin ratio, demonstrated the best resistance to various environmental stresses, making it a promising option for sustainable composite applications.
In clinical veterinary practice, even after the most painstaking physical examination, accurate diagnosis of cardiac diseases is often very difficult to arrive at. One of the tools for studying the disease conditions of the heart is electrocardiography (ECG) on which literature pertaining to buffaloes is very limited (Upadhyay and Rao, 1986). Electrocardiography provides a basis for accurate diagnosis of certain cardiac abnormalities. The major use of ECG in large animals is in the detection and diagnosis of conduction abnormalities and arrhythmic heart disease. These are detected by measurement of the various wave forms and intervals in ECG that represent conduction and depolarization of heart and by observation of their absence or abnormality (Gay and Radostits, 2000).
An experimental procedure adopted for measuring the erosive burning in solid propellants under transonic and supersonic crossflow Mach numbers is explained. Three formulations of ammonium perchlorate/hydroxyl-terminated-polybutadiene propellants of different burning rates (6, 9, and 16 mm/s at 5 MPa) were used for the study. The study presents the erosive burning results for a range of crossflow Mach numbers from 0.8 to 1.7. Additionally, the adopted experimental procedure clearly demonstrates the choking station movement in grain ports of nozzleless motors. As observed under subsonic crossflow conditions, in supersonic conditions the following conditions hold: 1) The erosive burning effect increases with the increase in both pressure and free stream velocity of crossflow. 2) The propellants with lower normal-burning rates experience greater erosive burning than those with higher normal-burning rates. Negative erosive burning under supersonic crossflow velocities is identified at low pressures.
This paper presents the design of a hybrid rocket motor and the experiments carried out for investigation of hybrid combustion and regression rates for a combination of liquid oxidiser red fuming nitric acid with solid fuel hydroxyl-terminated Polybutadiene. The regression rate is enhanced with the addition of small quantity of solid oxidiser ammonium perchlorate in the fuel. The characteristics of the combustion products were calculated using the NASA CEA Code and were used in a ballistic code developed for predicting the performance of the hybrid rocket motor. A lab-scale motor was designed and the oxidiser mass flow requirements of the hybrid motor for the above combination of fuel and oxidiser have been calculated using the developed ballistic code. A static rocket motor testing facility has been realised for conducting the hybrid experiments. A series of tests were conducted and proper ignition with stable combustion in the hybrid mode has been established. The regression rate correlations were obtained as a function of the oxidiser mass flux and chamber pressure from the experiments for the various combinations. Defence Science Journal, 2011, 61(6), pp.515-522 , DOI:http://dx.doi.org/10.14429/dsj.61.873
With their unique operational characteristics, hybrid rockets can potentially provide safer, lower-cost avenues for spacecraft and missiles than the current solid propellant and liquid propellant systems. Classical hybrids can be throttled for thrust tailoring, perform in-flight motor shutdown and restart. In classical hybrids, the fuel is stored in the form of a solid grain, requiring only half the feed system hardware of liquid bipropellant engines. The commonly used fuels are benign, nontoxic, and not hazardous to store and transport. Solid fuel grains are not highly susceptible to cracks, imperfections, and environmental temperature and are therefore safer to manufacture, store, transport, and use for launch. The status of development based on the experience of the last few decades indicating the maturity of the hybrid rocket technology is given in brief. Defence Science Journal, 2011, 61(3), pp.193-200 , DOI:http://dx.doi.org/10.14429/dsj.61.518
An experimental procedure adopted for measuring the erosive burning in solid propellants under transonic and supersonic crossflow Mach numbers is explained. Three formulations of ammonium perchlorate/hydroxyl-terminated-polybutadiene propellants of different burning rates (6, 9, and 16 mm/s at 5 MPa) were used for the study. The study presents the erosive burning results for a range of crossflow Mach numbers from 0.8 to 1.7. Additionally, the adopted experimental procedure clearly demonstrates the choking station movement in grain ports of nozzleless motors. As observed under subsonic crossflow conditions, in supersonic conditions the following conditions hold: 1) The erosive burning effect increases with the increase in both pressure and free stream velocity of crossflow. 2) The propellants with lower normal-burning rates experience greater erosive burning than those with higher normal-burning rates. Negative erosive burning under supersonic crossflow velocities is identified at low pressures.
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