485 Experimental Performance Evaluation of Small Solid Rocket Motor with Composite Case for Environmental Conditions Lokesh Srivastava, #, * L. Krishnanand, $ N. Kishore Nath # and D. Laxman # # DRDO - Advanced Systems Laboratory, Kanchanbagh, Hyderabad - 500058, India $ National Institute of Technology, Warangal, Telangana - 506004, India * E-mail: evergreenlok@gmail.com ABSTRACT Polymeric composites are widely used in aerospace. One such important use of polymeric composites is the flament-wound composite case for the Solid Rocket Motor (SRM). Environmental conditions expected during fight and other phases of the SRMs life cycle afect its performance. The performance of SRM, in turn, depends primarily on the composite case and propellant grain. In this study, the performance evaluation of SRM with the composite case is carried out for diferent environmental conditions. These cases are designed to sustain very high pressure and temperature environments generated due to the combustion of propellant grains and are intended to perform adequately at any time during their service life. The performance evaluation test matrix is formulated considering various expected dynamic and thermal conditions. The small SRM with a composite case is subjected to planned tests as per the matrix, followed by static tests. The pressure versus time data is plotted for all test conditions. The ballistic parameters result of the virgin (without subjecting it to any test) small SRM is considered as a reference for comparative studies with the rest of all other test conditions results. All the ballistic performance test results are also analysed with respect to the pressure-time curve for mission bounds. The analysis of experimental test results reveals that various environmental dynamic conditions like random vibration, acceleration and shock, do not afect the composite case and the ballistic performance of a small SRM. The efect of grain temperature on ballistic performance is also found as expected. Keywords: Composite case; Filament winding; Solid rocket motor; Environmental condition; Performance evaluation Received : 17 January 2022, Revised : 04 April 2022 Accepted : 21 April 2022, Online published : 01 July 2022 Defence Science Journal, Vol. 72, No. 3, May 2022, pp. 485-494, DOI : 10.14429/dsj.72.17863 © 2022, DESIDOC 1. INTRODUCTION The long-range missile systems are deployed and are kept in storage, subjected to handling and operational trials until they are used. Since these systems are principally strategic and mostly intended to be used once, their safe life post-deployment is always a matter of concern. The present-day state-of-the-art technology uses composites in various structural and thermal applications for missile and space applications 1 . Filament winding is one of the most prominent polymeric composite manufacturing methods, where resin impregnated continuous flaments are wound over a male rotating mandrel in a pre- described manner under tension to yield a surface of revolution with the desired thickness and ply sequences 2 . These products are ideally suited as a composite case for SRMs 2-3 . The in- service performance of the polymeric composite is sensitive to environmental factors 4-5 . Environmental conditions degrade the mechanical properties and efects the structural performance of polymeric composites 6-8 . The primary objective of this study is to qualify the SRM with composite cases for diferent service and operational conditions of missile systems such as vibration, acceleration, shock and temperature environments. The following are the environmental factors that may afect the performance: • Chemical and physically induced aging mechanisms due to long-term exposure to temperature and humidity • Mechanical factors (such as thermally induced stresses, shock loads, acceleration and vibrations) The above factors, afect the mechanical properties, thermal stability and efective service life of SRM. This SRM was designed to produce a high mass fow rate and high heat fux with an instantaneous pressure rise in the shortest possible time 9-10 . The composite case was designed to withstand very high pressure and temperature environments for a short period of time 1,9-10 . Accordingly, Hizli 4 examined the efect of environmental conditions on the structural performance of composite rocket motor cases using hydrostatic burst methods. However, the burst test does not simulate instantaneous pressure rise and combustion environments. On the contrary, a static test resembles actual operational conditions, as expected during fight. Unfortunately, in the available literature, eforts to understand the behaviour of the SRM exposed to diferent condition using static fring is extremely rare. Accordingly, the present study has been carried out on a subsystem level resembling the actual fight hardware confguration and the overall efect of environmental conditions on the performance of SRM with the composite case has been experimentally evaluated in an integrated way through static fring.