Multiscale modeling of heterogeneous propellants from particle packing to grain failure using a surface-based cohesive approach

In the present work, a computational framework is established for multiscale modeling and analysis of solid propellants. A packing algorithm, considering the ammonium perchlorate (AP) and aluminum (Al) particles as spheres or discs is developed to match the size distribution and volume fraction of solid propellants. A homogenization theory is employed to compute the mean stress and strain of a representative volume element (RVE). Using the mean results, a suitable size of RVE is decided. Without considering the interfaces between particles and matrix, several numerical simulations of the relaxation of propellants are performed. The relaxation effect and the nonlinear mechanical behavior of propellants which are dependent on the applied loads are discussed. A new technology named surface-based cohesive behavior is proposed to describe the phenomenon of particle dewetting consisting of two ingredients: a damage initiation criterion and a damage evolution law. Several examples considering contact damage behavior are computed and also nonlinear behavior caused by damaged interfaces is discussed in this paper. Furthermore the effects of the critical contact stress, initial contact stiffness and contact failure distance on the damaged interface model have been studied.