Continuum Modeling of Energetic Materials to Interpret Atomistic and Molecular Simulations for Advanced Design
Abstract
The design of energetic materials is a critical core technology, needed to make improvements to explosive warhead performance and to enhance lethality. Breakthrough performance might be achieved by material designs that can be manufactured in new ways. Invention of new explosive formulations requires a greater understanding of the complex mechanical and chemical processesin the condensed phase. It is important understand condensed phase chemistry and transport in more scientifically sophisticated ways, to control the energy release of initially separated reactive components.Our group has developed a multi-component model for materials that can simultaneously describe complex mechanics, phase change and chemistry coupling, when the material changes from solid to liquid to gas with underlying chemical changes. The model (dubbed the ~Gibbs formulation~) has its origins in classical physical chemistry and non-equilibrium, continuum thermodynamics, and is related to classical gas-phase combustion and phase transformation theory. One can choose components, precisely define stoichiometric kinetics mechanisms and systematically model the chemistry of explosives.ONR has previously funded the Stewart-group at the University of Illinois to develop a continuum (bridging) model that can precisely replicate most, if not all, of the averaged processes observed in atomistic simulations, that include molecular dynamics (MD), reactive molecular dynamics (RMD) and coarse-grained, dissipative particle dynamics (DPD). A powerful way to make progress is to use modern atomistic simulations, such as those afforded byRMD and DPD to study model chemistry, and then use associated continuum bridging theories to interpret the simulations. Once the atomistic and continuum bridge theories are linked, such that averages of the atomistic simulations are faithfully reproduced by the corresponding continuum simulations, the continuum model simulations can be used to optimize explosiveoutput. The Stewart-group has an extensive list of atomistic-based collaborators, with background in computational physical chemistry that use ReaxFF and DPD methods.We propose a 3-year effort with four basic tasks: Task I is the identification of tractable, reduced chemical kinetic mechanisms for explosives. Initial work will include the continued investigation of 4-component mechanism previously developed by the Stewart-group and collaborators, and investigation and comparison with the Schweigert chemical mechanism, developed fornitramines and other kinetics. Task II will be the simulation of energetic material mixture responses to externa"l shock, shear and thermal stimulus. These simulations will include 1) spatially and time-dependent, ""mirrored"" continuum simulation"s that correspond to atomistic simulations, and 2) meso-scopic continuum simulations of multi-material interactions between explosive constituents such as binders, and explosive crystallites, oxidizers and other material of interest to the Navy. Task III is the development of averaging theory for atomistic simulations to generate improved continuum descriptions, especially for reaction kinetics and transport. Task IV focuses on engineering level simulations to be carried out in collaboration with Navy labs, that can include: i) Detonation shock dynamics calibration of explosives, ii) Detonatorsimulation iii) Warhead simulation iv) Equation of state improvements for reactive flow.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 07, 2019
- Source ID
- N000141912084
Entities
People
- D. Scott Stewart
Organizations
- Office of Naval Research
- United States Navy
- University of Florida