Numerical study of solid propellant grains subjected to unsteady state thermal loading

Abstract

For an air-to-air missile system, the work environment contains steady and unsteady state thermal loading condition during shipment, storage and firing. Traditionally, the unsteady state thermal loading of solid propellant grains was not considered for simplifying the analytical task, and a steady state thermal loading assumption was analysed for structural integrity. But it does not mean that the unsteady state thermal loading is not useful and could be neglected arbitrarily, and this effect usually plays a very important role for determining the real critical area and obtaining a more reasonable result. In order to simulate the correct failure mode of thermoviscoelastic and incompressible polymer material design, concepts of transient heat transfer, time-temperature shift principle, cumulative damage theory and reduced integration were used. Under unsteady state thermal loading case, transient thermal and structural responses of solid rocket motor could be obtained, and one can see that those are dependent on time and location because of transient thermal loading. Results show that the unsteady state thermal loading case is important for structural integrity of solid propellant grains and improper negligence may obtain the incorrect failure mode and cause structural failure of missile system.