Computational studies of variations in Poisson's ratio for thermoviscoelastic solid propellant grains

Abstract

In this article, the results of an investigation on solid propellant grains considering the effect of Poisson's ratio v under thermal loading are presented. Traditionally the v value of solid propellant grains is assumed to be a constant (e.g. 0.4999) for engineer, but the real v value is dependent on the real chemical recipe design of solid propellant grains. In order to simulate the time-temperature-dependent behaviour of thermoviscoelastic propellants under various Poisson's ratios, concepts of the time-temperature shift principle and reduced integration were used for finite element simulation. Results show that the effect of Poisson's ratio is important for structural integrity of solid propellant grains because the type of polymer material is changed from incompressible ( v ≈ 0.5) to compressible ( v ≠ 0.5). Under thermal loading, the difference between the maximum principal thermal strains for v = 0.4999 and v = 0.470 is 68.8 per cent, that between the maximum principal thermal stresses for v = 0.4999 and v = 0.470 is 73.5 per cent and that between the maximum shear thermal stresses for v = 0.4999 and v = 0.470 is 74.8 per cent. In addition, there are differences in the quasi-elastic analysis because the effect of Poisson's ratio becomes more and more predominant as the material type of solid propellant grains changed from incompressible to compressible.