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.

Detailed studies on the formation of piezoelectric β-phase of PVDF at different hot-stretching conditions

Abstract: The β-phase of polyvinylidene fluoride (PVDF) is well known for its piezoelectric properties. PVDF films have been developed using solvent cast method. The films thus produced are in β-phase . The β-phase films are transformed to piezoelectric β-phase , when films are hot-stretched at different temperature, and with different stretching factors. Films are characterized for structural, tensile and surface morphological changes during the transformation from α- to β-phase by using X-ray diffraction, differential scanning calorimeter, Raman spectra, Infrared spectra, tensile testing, and scanning electron microscopy. The films showed increased crystallinity with stretching up to 80oC. The optimum conditions to achieve β-phase have been discussed in detail. The fabricated PVDF sensors have been tested for free vibration and impact on plate structure, and its response is compared with conventional piezoelectric wafer type sensor. The resonant and anti-resonant peaks in the frequency response of PVDF sensor match well with that of PZT.

Optical Air Flow Measurements for Flight Tests and Flight Testing Optical Air Flow Meters

Abstract: Optical air flow measurements can support the testing of aircraft and can be instrumental to in-flight investigations of the atmosphere or atmospheric phenomena. Furthermore, optical air flow meters potentially contribute as avionics systems to flight safety and as air data systems. The qualification of these instruments for the flight environment is where we encounter the systems in flight testing. An overview is presented of different optical air flow measurement techniques applied in flight and what can be achieved with the techniques for flight test purposes is reviewed. All in-flight optical airflow velocity measurements use light scattering. Light is scattered on both air molecules and aerosols entrained in the air. Basic principles of making optical measurements in flight, some basic optical concepts, electronic concepts, optoelectronic interfaces, and some atmospheric processes associated with natural aerosols are reviewed. Safety aspects in applying the technique are shortly addressed. The different applications of the technique are listed and some typical examples are presented. Recently NASA acquired new data on mountain rotors, mountain induced turbulence, with the ACLAIM system. Rotor position was identified using the lidar system and the potentially hazardous air flow profile was monitored by the ACLAIM system.

Studies on Hydroxyl Terminated Polybutadiene Toughened Phenolic Resin

Abstract: Phenolic novolac was modified with hydroxyl terminated polybutadiene (HTPB) using resole as compatibilizer. These systems were characterized by differential scanning calorimetry, and IR analysis. Neat resin castings were prepared with varying percentages of HTPB. The fracture toughness of these systems was assessed by evaluating the critical stress intensity factor (K lt;subgt;Iclt;/subgt;) using single-edge notch, three-point bend specimens. The fracture behavior was characterized by scanning electron microscopy. These studies revealed that the fracture toughness of the phenolic novolac resin was improved by blending it with HTPB due to the formation of a heterogeneous phase with minute particles of elastomer, which arrests the propagation of cracks.