Multiscale Damage Modeling of Solid Propellants:
From Particle Packing to Failure

K. Matouš, H.M. Inglis, X. Gu, T.L. Jackson

Center for Simulation of Advanced Rockets
University of Illinois at Urbana-Champaign
Urbana, IL 61801 USA

D. Rypl

Department of Structural Mechanics
Faculty of Civil Engineering
Czech Technical University in Prague
Thákurova 7, 166 29 Prague, Czech Republic

P.H. Geubelle

Department of Aerospace Engineering
University of Illinois at Urbana-Champaign
Urbana, IL 61801 USA


We present a theoretical and computational framework for modeling the multiscale constitutive bahaviour of highly filled elastomers, such as solid propellants and other energic materials. Special emphasis is placed on the effect of the particle debonding or dewetting process taking place at the microscale and on the macroscopic constitutive response. The microscale is characterized by a periodic unit cell, which contains a set of hard particles (such as ammonium perchlorate for AP-based propellants) dispersed in an elastomeric binder. The unit cell is created using a packing algorithm that treats the particles as spheres or discs, enabling us to generate packs which match the size distribution and volume fraction of actual propellants. A novel technique is introduced to characterize the pack geometry in a way suitable for meshing allowing for the creation of high-quality periodic meshes with refinement zones in the regions of interest. The proposed numerical multiscale framework, based on the mathematical theory of homogenization, is capable of predicting the complex, heterogeneous stress and strain fields associated, at the microscale, with the nucleation and propagation of damage along the particle matrix interface, as well as the macroscopic response and mechanical properties of the damaged continuum. Examples involving simple unit cells are presented to illustrate the multiscale algorithm and demonstrate the complexity of the underlying physical processes.