| || Performance Evaluation and Experimental Studies on Metallised Gel Propellants
Author : Krishnamurthy, V.N. ;Ninan, K.N.;Rao, S.S.;Subramanian, S.;Thanki, K.P.;Prabhakaran, N.;Varghese, T.L.
Source : Defence Science Journal ; Vol:49(1) ; 1999 ; pp 71-78
Subject : 662.3 Propellants;66 Chemical Technology
Keywords : Thixotropic behaviour ;Burst pressure tests;Bulk density;Pseudoplastic behaviour;Gel propellants;Liquid propellants
Abstract : "Metallised gel propellants offer higher specific impulse and volumetric loading, reduced vaporisation loss, spillage and slosh problems and easy storage in comparison to the conventional liquid propellants. Theoretical performance analysis of gel propellant containing Al in unsymmetrical dimethyl hydrazine-dinitrogen tetroxide (UDMH-N/sub 2/O/sub 4} system shows peak Isp (vacuum condition) of 316.7 s and 318.3 s at oxidiser/fuel (O/f) ratios of 1.5 and 1.0, respectively for 30 per cent and 40 per cent UDMH-Al gel propellants, under standard conditions. The effect of other parameters like area ratio and chamber pressure on performance has been brought out in view of mission oriented applications. Aluminium has been found to be a better choice over magnesium in metallised gel propellants. Experimental studies on UDMH gellation using propellant grade (15 micrometer)and pyrotechnic grade (1.5 micrometer)Al in 500g batch level show that gellant(methyl cellulose) concentration could be reduced by 50 percent using pyrotechnic grade Al. The pseudoplastic-thixotropic behaviour, flow rate through die holes, burst pressure tests and bulk density are studied. UDMH -25 to 30 per cent Al gels with both grades of Al are found to be stable, pseudoplastic (shear thinning) and thixotropic (time-dependent shear thinning), but their flow pattern through die holes differ in nature. "
| || Carbon Carbon Composites: An Overview
Author : Devi, G. Rohini;Rao, K. Rama
Source : Defence Science Journal ; Vol:43(4) ; 1993 ; pp 369-383
Subject : 678 Composite Materials
Keywords : Pseudoplastic behaviour;Inverse composite;Aircraft brake discs;Material characterisation
Abstract : Carbon carbon composites are a new class of engineering materials that are ceramic in nature but exhibit brittle to pseudoplastic behaviour. Carbon-carbon is a unique all-carbon composite with carbon fibre embeded in carbon matrix and is known as an inverse composite. Due to their excellent thermo-structural properties, carbon-carbon composites are used in specialised application like re-entry nose-tips, leading edges, rocket nozzles, and aircraft brake discs apart from several industrial and biomedical applications. The multidirectional carbon-carbon product technology is versatile and offers design flexibility. This paper describes the multidirectional preform and carbon-carbon process technology and research and development activities within the country. Carbon-carbon product experience at DRDL has also been discussed. Development of carbon-carbon brake discs process technology using the liquid impregnation process is described. Further the test results on material characterisation, thermal, mechanical and tribological properties are presented.