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Institution

Vikram Sarabhai Space Centre

FacilityThiruvananthapuram, India
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.


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Journal ArticleDOI
TL;DR: In this paper, the shape memory properties of DGEBA/PTAC/PMDA blends were investigated by differential scanning calorimetry and FTIR and the results showed that PTAC increased the modulus ratio which in turn increased the extent of shape recovery with a concomitant diminution in the shape recovery time.
Abstract: Thermoset polymers exhibiting shape memory properties were derived on reacting digycidyl ether of bisphenol A (DGEBA) with pyromellitic dianhydride (PMDA) in presence of a shape memory polymer precursor i.e. carboxyl telechelic poly(tetramethylene oxide) (PTAC) that was synthesized. Cure characteristics of the blends were investigated by differential scanning calorimetry and FTIR. Blends with varying proportions of DGEBA/PTAC/PMDA were studied for their flexural, dynamic mechanical and shape memory properties. The flexural strength and modulus decreased with increase in concentration of PTAC. The storage modulus and the transition temperatures (Ttrans) of the systems also showed a similar trend. These polymers showed good shape memory properties. PTAC increased the modulus ratio (Eg/Er) which in turn increased the extent of shape recovery with a concomitant diminution in the shape recovery time. An increase in temperature results in faster recovery with an increase in the extent of shape recovery. The epoxy-anhydride system possesses adequate thermal, mechanical and shape memory characteristics for possible use in smart actuator systems.

31 citations

Journal ArticleDOI
TL;DR: In this paper, the properties of polybenzoxazine filled with chopped silica fibers and their syntactic foams of varying composition and densities were investigated, including tensile, compressive, and flexural properties with change in composition.
Abstract: Polybenzoxazine filled with chopped silica fibers and their syntactic foams of varying composition and densities were processed. The composition and density variations were achieved by regulating the relative concentrations of silica fiber and glass microballoons (MB). The variation of tensile, compressive, and flexural properties with change in composition was investigated. For the silica-fiber filled materials, the property attained a maximum at about 40% volume content of fiber, and thereafter, the properties showed a diminishing trend. The incorporation of microspheres significantly lowered the strength of silica filled materials. However, the decrease in the specific flexural strength was less pronounced and the strength was unaffected beyond a certain microsphere content. During processing and mechanical testing, a large quantity of fibers was fractured, which reduced the strength of silica filled systems. The diminution in material strength on embedding microspheres is attributed to the presence of stress concentrating loci as evidenced from SEM analysis. The various factors leading to the property variation with composition are discussed with microscopic analyses, like clustering of fibers, crack propagation, fiber pull out, and debonding of fibers from resin phase. Dynamic mechanical analysis revealed an improved damping property for the filled materials in contrast to the unfilled polymer. The Tg (deduced from tan δ maximum from DMTA) decreased in silica fiber containing materials and on incorporating the MB, the values reverted back to that of the neat polymer. Both silica and MB conferred better thermal and thermooxidative stabilities to the polybenzoxazine. However, the degradation mechanism is nonoxidative in nature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

31 citations

Journal ArticleDOI
TL;DR: The thermal decomposition of copper ammonium chromate (CAC), a precursor of copper chromite (CC) catalyst used as a ballistic modifier in solid propellants, has been thoroughly studied in this paper.

31 citations

Journal ArticleDOI
TL;DR: In this article, a more comprehensive spectral model based on charge exchange induced X-ray emission by ions precipitating into the Jovian atmosphere is used to provide new understanding of the polar auroras.
Abstract: Expanding upon recent work, a more comprehensive spectral model based on charge exchange induced X-ray emission by ions precipitating into the Jovian atmosphere is used to provide new understanding of the polar auroras. In conjunction with the Xspec spectral fitting software, the model is applied to analyze observations from both Chandra and XMM-Newton by systematically varying the initial precipitating ion parameters to obtain the best fit model for the observed spectra. In addition to the oxygen and sulfur ions considered previously, carbon is included to discriminate between solar wind and Jovian magnetospheric ion origins, enabled by the use of extensive databases of both atomic collision cross sections and radiative transitions. On the basis of fits to all the Chandra observations, we find that carbon contributes negligibly to the observed polar X-ray emission suggesting that the highly accelerated precipitating ions are of magnetospheric origin. Most of the XMM-Newton fits also favor this conclusion with one exception that implies a possible carbon contribution. Comparison among all the spectra from these two observatories in light of the inferred initial energies and relative abundances of precipitating ions from the modeling show that they are significantly variable in time (observation date) and space (north and south polar X-ray auroras).

31 citations

Journal ArticleDOI
TL;DR: In this article, the effects of large deflection and inplane forces on flutter boundary is included, based on convergence study an eight element solution is given for all the results presented.

31 citations


Authors

Showing all 2111 results

NameH-indexPapersCitations
M. Santosh103134449846
Sabu Thomas102155451366
S. Suresh Babu7049817113
K. Krishna Moorthy542639749
Sathianeson Satheesh5317211099
M. Y. Hussaini4920716794
J.R. Banerjee441465620
C. P. Reghunadhan Nair371814825
K. N. Ninan361594156
Anil Bhardwaj352304527
Ivatury S. Raju331216626
Venkata Sai Kiran Chakravadhanula321023011
P.K. Sinha321182918
J.-P. St.-Maurice311133446
Subramaniam Gopalakrishnan281232951
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202313
202230
2021186
2020160
2019149
2018136