The Ohio State University

Full Title:

Computational modeling of heterogeneous solid propellants:From micro‐tomography to material failure and combustion 

Abstract:

In the presentation, I will discuss an efficient and accurate analysis of chemo‐thermo‐mechanical material behavior, which relies on a hierarchical multi‐scale modeling concept to describe accurately physical phenomena such as damage evolution and nonlinear viscoelastic response of heterogeneous solid propellants. An adaptive multi‐scale methodology will be presented, which creates a hierarchy of computational subdomains with varying resolution for multiple‐level and multi‐physics problems. The theory introduces a hierarchy of models and differentiates between non‐critical and critical regions, and ranges from macroscopic computations using continuum constitutive equations to detailed zooming for pure microscopic simulations. I will also talk about the multi‐physics coupling between themomechanical processes and combustion.

The combustion of heterogeneous solid propellants is modeled by including a fluid domain over the solid surface, in which the related physical phenomenon, namely, fluid transport and chemical reactions are introduced. The chemical reactions, occurring in the fluid phase and on the regressing solid‐fluid interface, are described by a three‐step kinetics model and an Arrhenius equation. The transport of the gaseous species generated by the chemical reactions is modeled by the species equation (mass conservation) and a Petrov‐Galerkin method is used to solve these equations due to the presence of convective terms. The velocity/momentum of the gas phase is required to calculate the convective flux and is obtained by using the Oseen model.

Any serious attempt to model a heterogeneous system, such as a heterogeneous propellant, must also include a strategy for constructing a complex computational domain. In the talk, I will delineate a procedure based on an evolutionary optimization to construct a unit cell with the same statistics (n‐point probability functions) to that of the original material, which is tomographically characterized. Our current micro‐CT instrument provides tomographic imaging of material structure with ~1 μm and ~30 nm resolution, resulting in a direct link between experimental observations and the material system. However, both micro‐CT and nano‐CT can become much more powerful tools by combining them with the quantitative abilities. The resulting stress‐strain measurements and displacement data, although limited to moderate levels of quasi‐static thermal and mechanical loads, are providing an unprecedented detail of fully 3D deformation field, including in situ damage propagation, for complete comparison with the corresponding simulations.

Bio:

Karel Matous is a principal research scientist at the Computational Science and Engineering (CSE) and an adjunct assistant professor at the Department of Aerospace Engineering at the University of Illinois at Urbana‐Champaign. He received his M.S. and Ph.D. in Theoretical & Applied Mechanics from the Czech Technical University in Prague. Before coming to the University of Illinois he was a postdoctoral associate at the Rensselaer Polytechnic Institute. He currently leads the computational physics team as the part of the Advanced Simulation and Computing (ASC) Program at CSE. His research group focuses on advanced computational mechanics, advanced numerical methods and multi‐scale/multi‐time/multi‐physics modeling of complex heterogeneous materials and systems, such as solid propellants, metal alloys and advanced self‐healing adhesives. He is involved in several interdisciplinary research programs with funding from various agencies. Dr. Matous received Rector's award for the best Ph.D. students from the Czech Technical University in Prague and his student, Mohan Kulkarni (Ph.D. candidate AE, Prof. Geubelle coadviser), won the student presentation competition in the material modeling specialty area at the 9th US National Congress on Computational Mechanics (USNCCM9) in San Francisco. Recently an article from Dr. Matous' group entitled "Multiscale cohesive failure modeling of heterogeneous adhesives" published in Journal of the Mechanics and Physics of Solids has been featured on ScienceDirect Top 25 Hottest articles in April‐June 2008. He is a member of ASME, ASCE, AIAA, USACM and IACM.

The seminar will be held in E001 Scott Laboratory.