Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

Multi-response mathematical modelling, optimization and prediction of weld bead geometry in gas tungsten constricted arc welding (GTCAW) of Inconel 718 alloy sheets for aero-engine components

Abstract: The gas tungsten constricted arc welding (GTCAW) parameters namely Main Current, Delta Current, Delta Current Frequency and Welding Speed were optimized to obtain full penetration and optimum weld bead geometry using Response Surface Methodology (RSM) to join thin Inconel 718 alloy sheets (2 mm thick). Empirical relationships were formulated to predict the weld bead characteristics such as width of bead, depth of penetration, width of heat affected zone (HAZ) and area of fusion zone (FZ). The weld bead characteristics were predicted with good accuracy using developed empirical relationships. The direct and interaction effect of GTCAW parameters on weld bead geometry is discussed in this paper.

Synthesis and properties of poly ether nitrile sulfone copolymers with pendant methyl groups

Abstract: Poly ether nitrile and poly ether nitrile sulfone copolymers with pendant methyl groups were prepared by the nucleophilic substitution reaction of 2,6′-dichlorobenzonitrile with methyl hydroquinone and with varying mole proportions of methyl hydroquinone and 4,4′dihydroxydiphenylsulfone using N-methyl pyrrolidone as solvent in the presence of anhydrous K2CO3. The polymers were characterized by different physicochemical techniques. Copolymer composition was determined using FTIR technique. Thermogravimetric data reveals that all the polymers were stable up to 420°C with a char yield above 40% at 900°C in N2 atmosphere. The glass transition temperature was found to increase and the activation energy and inherent viscosities were found to decrease with increase in concentration of the 4,4′-dihydroxydiphenylsulfone units in the polymer. Trimerization reactions are found to be favorable with increase in concentration of methyl hydroquinone units in the polymer. Crystallinity of the polymer was also studied using wide angle X-ray diffraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1303–1309, 2006

Graphene oxide induced fast curing of amino novolac phthalonitrile

Abstract: Graphene oxide (GO) possessing hydroxyl and epoxy groups was synthesized by a modified Hummer's process and was found to conform to the empirical formula C0.801[epoxy]0.190[OH]0.009. GO was examined as a curative for amino novolac phthalonitrile (APN). It was found to facilitate the crosslinking reaction by acting as a reactant for the amino group. Additionally, epoxy and OH groups in GO react with the nitrile groups of APN providing another pathway for facilitating the curing of APN. Epoxy groups in GO react with the nitrile groups of APN in the presence of OH groups (generated by the epoxy–amine reaction), facilitating the crosslinking at a lower curing temperature. Blending with GO decreases the overall curing temperature of APN. The co-reaction of the two systems led to a single phase matrix whose failure mode changed from brittle to ductile with no penalty in the thermal stability.