Slow Cook-Off Simulation of PBX Based on RDX

Abstract

Cook-off tests are commonly used to assess thermal behaviour of energetic materials under external thermal stimuli. Numerical simulation became a powerful tool to reduce the costs with experimental tests. However, numerical simulations are not able to predict the violence of thermal response, but instead accurately reproduce radial heat flow in the test vehicle and satisfactorily predict the delay time to ignition and ignition temperature. This paper describes the slow cook-off simulation of 3 selected PBX based on RDX in a small-scale test vehicle, using the equilibrium equation of Frank-Kaminetskii and testing 2 kinetic models: Johnson-Mehl-Avrami (n) and Šesták-Berggren (m, n). The influence of successive addition of binder elements (HTPB, DOS, and IPDI) on slow cook-off results of selected PBX was assessed. The variation of ±10% in input data was performed to determine the influence on the slow cook-off results. Results showed that the addition of binder elements reduces the delay time to ignition as well as ignition temperature and that the Šesták-Berggren (m, n) kinetic model generates smaller values and with less deviation linked to the variation of input data. The selection of kinetic model as well as the variation of ±10% in input data had a negligible influence on the slow cook-off results of cured PBX.