National Aerospace Laboratories

About: National Aerospace Laboratories is a facility organization based out in Bengaluru, India. It is known for research contribution in the topics: Coating & Corrosion. The organization has 1838 authors who have published 2349 publications receiving 36888 citations.

Concurrent studies on braided and filament wound carbon fiber composites – a comparative appraisal

Abstract: Braided and filament wound CFRP were fabricated with varied fiber orientations. These composites exhibited not only similar trends in their experimental strength and stiffness properties but also good correlations with predictions made by CLT.

A comparative study of failure features in aerospace grade unidirectional and bidirectional woven CFRP composite laminates under four-point bend fatigue loads

Abstract: Damage mechanisms in unidirectional (UD) and bi-directional (BD) woven carbon fiber reinforced polymer (CFRP) laminates subjected to four point flexure, both in static and fatigue loadings, were studied. The damage progression in composites was monitored by observing the slopes of the load vs. deflection data that represent the stiffness of the given specimen geometry over a number of cycles. It was observed that the unidirectional composites exhibit gradual loss in stiffness whereas the bidirectional woven composites show a relatively quicker loss during stage II of fatigue damage progression. Both, the static and the fatigue failures in unidirectional carbon fiber reinforced polymer composites originates due to generation of cracks on compression face while in bidirectional woven composites the damage ensues from both the compression and the tensile faces. These observations are supported by a detailed fractographic analysis.

Studies on the oxygen sensitivity and microstructure of sol–gel based organic–inorganic hybrid coatings doped with platinum porphyrin dye

Abstract: Hybrid organic–inorganic nanocomposite coatings were prepared by copolymerizing tetraethylorthosilicate with ethyltriethoxysilane with an acid catalysis process. Oxygen sensor coatings were fabricated by doping the hybrid sol with platinum meso-tetra(pentfluorophenyl) porphyrin. Photophysical properties and oxygen sensitivity of the sensor coatings were studied. The microstructure of the coatings was examined using optical microscopy and scanning electron microscopy. The effect of sol–gel process conditions like precursor silane molar ratio, acid concentration and stirring time of the sol on the oxygen sensitivity and surface microstructure of the sensor coating was studied. Oxygen sensitivity and surface morphology of the coatings were dependent on the sol–gel process parameters.

Effect of penetrants on the aramid Nomex

Abstract: The response of Nomex sheets to some penetrants has been analyzed. The process of moisture uptake depends on the relative humidity (RH) of the ambient atmosphere and the initial characteristics of the polymer. In the case of common laboratory solvents,the uptake by the polymer shows an inverse dependence on the molar volume of the former. Although the calendered and the uncalendered Nomex sheets exhibit an overall similarity in their response to various penetrants,quantitative comparison reveals distinct differences.

Silica-alumina based sol-gel coating containing cerium oxide nanofibers as a potent alternative to conversion coating for AA2024 alloy

Abstract: The current work demonstrates a study on the improved corrosion protection efficiency of a defect-free sol-gel hybrid coating consisting of cerium oxide nanofibers vis-a-vis sol-gel coating containing commercial nanosize ceria particles as corrosion inhibitors. The less researched organically modified silica-alumina (Si-Al) hybrid sol-gel coating containing cerium oxide nanofibers and commercial ceria are synthesized from 3-glycidoxypropyltrimethoxysilane and aluminum-tri-sec-butoxide. The sol-gel matrix containing cerium oxide nanofibers exhibiting Ce mainly in +3 oxidation state exhibits improved corrosion resistance as corroborated by electrochemical impedance spectroscopy. The corrosion property of this sol-gel coating commensurates well with the conventional chromate conversion coating (CCC) as evidenced by the neutral salt spray test. The developed coating exhibits good compatibility with the top primer layer and thus ascertains that the developed Si-Al based sol-gel coating containing cerium oxide nanofibers is a potent alternative to conventional CCC.