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
Abstract:
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.