Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Mach number & Turbulence. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Novel glass fabric-reinforced polybenzoxazine–silicate composites with polyvinyl butyral for high service temperature applications

Abstract: The aim of this study is to develop novel glass fabric-reinforced polybenzoxazine–silicate composites with enhanced performances, which can overcome the disadvantages related to the low crosslink density of glass fabric-reinforced polybenzoxazine composites. Glass polybenzoxazine silicate composites were prepared via the copolymerization of bisphenol F benzoxazine using glass fabric, polyvinyl butyral as the coupling agent and various ratios of ethyl silicate. FTIR and DSC were utilized to study the chemical reactions and curing optimization, respectively. It was found that complete polymerization occurred at 200 °C. DMA analysis of the prepared glass polybenzoxazine silicate composites showed enhanced stiffness, crosslink density, service temperature, and network branching with uniform phase distribution. The thermal oxidative decomposition temperatures and char yield obtained by TGA and interfacial adhesion by SEM for glass polybenzoxazine silicate composites were found to be improved when compared to that of the glass polybenzoxazine composites. The composites prepared by this method showed enhanced service temperature, stiffness, crosslink density, thermal oxidative resistance, and char yield when compared to glass fabric-reinforced homopolymerized polybenzoxazine composites. These newly developed glass polybenzoxazine silicate composites are promising materials to overcome various shortcomings associated with polybenzoxazine and other traditional resin composites.

A Singular Perturbation Based Midcourse Guidance Law for Realistic Air-to-Air Engagement

Abstract: In this study, a singular perturbation based technique is used for synthesis and analysis of a near optimal midcourse guidance law for realistic air-to-air engagement. After designing the proposed midcourse guidance law using three dimensional point mass formulation it has been validated through detailed realistic six degrees of freedom simulation. During terminal phase only proportional navigation guidance have been used. The calculation of optimal altitude in present guidance law has been carried out using Newton’s method, which needs generally one iteration for convergence and suitable for real-time implementation. Extended Kalman filter based estimator has been used for obtaining evader kinetic information from both radar and seeker noisy measurements available during midcourse and terminal guidance. The data link look angle constraint due to hardware limitation which affects the performance of midcourse guidance has also been incorporated in guidance law design. Robustness of complete simulation has been carried out through Monte Carlo studies. Extension of launch boundary due to singular perturbation over proportional navigation guidance at a given altitude for a typical engagement has also been reported.

Comparison of the Radar and Seeker Modes of Pursuer Guidance

Abstract: This paper compares closed-loop performance of seeker-based and radar-based estimators for surface-to-air interception through 6-degree-of-freedom simulation using proportional navigation guidance.Ground radar measurements are evader range, azimuth and elevation angles contaminated by Gaussian noise. Onboard seeker measurements are pursuer-evader relative range, range rate also contaminated by Gaussian noise. The gimbal angles and line-of-sight rates in the gimbal frame,contaminated by time-correlated non-Gaussian noise with realistic numerical values are also available as measurements. In both the applications, extended Kalman filter with Gaussian noise assumption are used for state estimation. For a typical engagement, it is found that,based on Monte Carlo studies, seeker estimator outperforms radar estimator in terms of autopilot demand and reduces the miss distance.Thus, a seeker estimator with white Gaussian assumption is found to be adequate to handle the measurements even in the presence of non-Gaussian correlated noise. This paper uses realistic numerical values of all noise parameters.

A survey of ion implantation techniques for enhanced property modification for tailored materials

Abstract: The paper describes the various methods that have been developed for property modification of materials. Methods include ion implantation, sputtering and combination processes. Applications are listed with particular reference to semi-conductors.

Design of 8×8 Circularly Polarized planar array antenna for ISM band

Abstract: This work presents the design of 8×8 Circularly Polarized planar array antenna for 24 GHz ISM band to produce a narrow pencil beam of 12o–15o beamwidth which is compact enough to be placed onboard for airborne defence application This paper enumerate the design of single feed corner truncated circularly polarized microstrip patch antenna with Type A perturbation The design considerations of the single microstrip patch was carried forward for the design and simulation of 8×8 planar array antenna of maximum beamwidth 15o and scan angle 45o Comparison of the characteristics of single microstrip patch and planar array antenna was carried out with the simulation in IE3D The simulation results of planar array antenna shows the gain of 197 dBi, VSWR=106 ( 20 MHz, axial ratio of 11dB (< 3 dB) at resonant frequency of 2412565 MHz, meeting the requirement