Initiation and Post-Detonation Kinetics of Aluminized RDX Composites Using a First-principles Guided Multiscale Approach
Abstract
The objectives of the proposed effort is to develop a multiscale model of polymer-bonded Aluminized High Explosives (AHE) to understand the fundamental science and to answer many open scientific questions regarding role of Al in pre- and post-detonation chemical reactions. On completion of multiscale integration, role of microstructure in the performance of the AHE can be investigated using first-principles calculated kinetics of condensed/gas-phase reactions in high-pressure/temperature conditions. The approach is a stepwise development of a multiscale quantum-classical framework for initiation, ignition and post-detonation kinetics of aluminized polymer bonded energetic material. In this case, RDX is used as a model energetic material. The binders used in the simulations are DOA and HTPB. The results will be used to analyze the events leading to initiation and the propagation of hot spots in alpha and gamma RDX phases. On successful implementation, the following will be key impact of the work: Fundamental atomistic insights on decomposition mechanisms: The initiation and propagation of hot spot in PBX are in general poorly understood. Aluminum introduces further complexity to the initiation and propagation of reactions in the composite. Insights on the mechanisms for initiation of RDX including the role of Al will uncovered. Hot spot initiation and growth: Using DOD high-performance computing (HPC) environment, a new way to ignite different phases of RDX in RMD simulation to develop a full kinetic model will be developed. The benefit of triggering a reaction front using RMD simulations has general applicability to all HE systems and have been tested to work for FOX-7 and TATB systems. A detailed analysis of time-, temperature-, pressure- and composition-dependent chemistry from the RMD trajectories is a significant achievement for the field to connect mesoscale hot spot growth kinetics to broader issues in safety and C-WMD performance objectives. Beginning of a mesoscale model: A complete mesoscale model with Al/Al2O3/RDX, RDX/HTPB and other possible combination need to include many complex transport and reaction propagation steps. The biggest unresolved challenge for connecting atomistic simulations to mesoscale reaction-diffusion model is the lack of a data set that can be used with confidence to parameterize the propagation of hot spot to larger length and time scales. The applicability of extending the kinetics of major RDX dissociation channels are currently being compared with predictions from reactive molecular dynamics. The proposed effort intends to address the grand challenge of extending the results from reactive MD simulations from nanoseconds to microseconds by simplifying the chemistry for mesoscale continuum methods. The chemistry will be applied to detonation and void-collapse studies in collaboration with other research groups. Deflagration-to-detonation transition (DDT): DDT is another important aspect where non-ideal explosives such as AHE differs significantly from ideal explosives. In an ideal explosive, reactions kinetics can be explained using Chapman–Jouget (CJ) theory for detonations and can reproduce experimental results well using standard equations of states (EOS). Non-ideal explosives, however, have significant deviations from equilibrium kinetics. At the molecular level, the Al-phase is not mixed with the HE phase; therefore, the non-ideal behavior is often due to presence of metallic Al both in condensed phase, and more importantly, in the gas-phase post-detonation product. Baer et al. and others have successfully shown multiphase description of DDT is important. The proposed effort will explicitly consider the role of Al particles in condensed-phase and gas-phase reaction in determining macrokinetics and energy release in AHE. This will open the possibility for DTRA to investigate compositions with specific energy release characteristics for counter-WMD applications.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 26, 2016
- Source ID
- HDTRA11510034
Entities
People
- Santanu Chaudhuri
Organizations
- Defense Threat Reduction Agency
- University of Illinois Urbana–Champaign