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Modeling and Simulation of Structural Energetic Materials

Description:

TECHNOLOGY AREA(S): Weapons

OBJECTIVE: Develop and implement models and software tools to describe the coupled solid dynamics, interfacial phenomena and chemical reactions in energetic solid materials with heterogeneous (solid-solid-void systems) meso-structures.

DESCRIPTION: Coupling between structural dynamics and chemical reactions is a complex, challenging phenomena; understanding such phenomena through advanced modeling and simulation is crucial to the design of cutting-edge and emerging explosives (with controlled sensitivity and lethality), multifunctional materials (such as structural energetics) and porous reactive materials. The interaction of energy deposition mechanisms, including dynamic mechanisms such as shock compression and chemical mechanisms and reactive heat release is a complex phenomenon that challenges modeling efforts. This is due in part to the rather stiff spatial and temporal conditions inherent in these highly nonlinear and fast transient processes. Energy deposition can be spatially localized with a wide range of time scales (structural dynamic, wave propagation and reaction scales) that require extremely fine spatial and time discretization. At the mesoscale, in addition the various phases comprising the heterogeneous material can interact at interfaces and such phenomena may in fact be key to the response of the material to imposed loads. Thus, several challenging physical mechanisms and material characteristics have to be modeled and accurately represented in a simulation of the meso-scale mechanics of reactive heterogeneous systems. Furthermore, to enable computations within reasonable times, spatial and temporal adaptivity of the mesh is essential and parallel computation is imperative.

In particular the following issues represent the required modeling/software development efforts:

    • Interaction of particles embedded in a condensed phase with imposed shock conditions.

    • Interaction of particles with compressible flow in gases.

    • Reactive processes in the condensed and gas phases and their coupling with the stress and deformation fields in the meso-structures.

  • Interfacial phenomena including deformation, fracture and localized phenomena such as inter-particle friction and contact.

A further challenge to the model in systems that are employed in real-world applications is the interaction of energy bearing flows with “targets” or other incidental obstacles. Here the main question is the effect of a flow containing energy-bearing or energy-releasing material when a target is encountered. In many applications, it is necessary to calibrate or design the delivery of energy to targets in a pre-determined and controlled manner. To do this, one must accurately model the dynamics of material-momentum-energetic flows and flow-interface interactions.

Due to reductions in numbers and sizes of platforms across the services, there is a growing requirement for internal carriage of smaller, higher lethality munitions. One way to increase lethality while reducing munition size is by minimizing non-reactive parasitic weight through the use of structural energetics. Accurate modeling and simulation tools are critical in the design process in order to avoid over reliance on expensive experimentation. This topic directly supports both the Air Superiority and Global Precision Attack Core Function Master Plans.

PHASE I: Identify specific chemical reaction models and approach to developing the models. Model and solve the coupled system of equations describing the structural dynamics at high strain rates and loading conditions and its coupling with the chemical energy released during reactions. Identify the key input properties required and the diagnostic approach to obtaining them.

PHASE II: In Phase II, the models will be further developed and implemented in a computer-based tool, key input properties will be determined (by theory or experiment), and the capability to provide insights to the response of a material to a set of realistic insults will be demonstrated.

PHASE III DUAL USE APPLICATIONS: Application includes formulation of explosives and design of new materials such as structural energetics. The models and tools could also be applied to materials such as propellants. Results should be transitionable to all DOD services as well as the DoE, NASA and their supporting contractors.

REFERENCES:

    • Nesternko, V. F., Chiu, P-H, Braithwaite, C. H., Collins, A., Williamson, D. M., Olney, K. L., Benson, D., McKenzie, F., 2012, “Dynamic behavior of particulate/porous energetic materials,” AIP Conference Proceedings, Volume 1426, pp. 533-538.

    • Baer, M.R. 2000 Computational modeling of heterogeneous reactive materials at the mesoscale. Shock compression of condensed matter—1999 (eds. Furnish, M.D. Chhabildas, L.C. & Hixson, R.S.), pp. 27–33, Melville, NY: American Institute of Physics.

    • Chang H & Nakagaki M. 2001 Modeling of particle dispersed composite with meso-scale delamination or sliding. Nippon Kikai Gakkai Zairyo Rikigaku Bumon Koenkai Koen Ronbunshu, pp 563-564(2001).

    • Benson, D. J. and Conley, P., “Eulerian finite-element simulations of experimentally acquired HMX microstructures,” Modeling Simul. Mater. Sci. Eng., Vol. 7, pp. 333-354 (1999).

  • Conley, P. A., “Eulerian hydrocode analysis of reactive micromechanics in the shock initiation of heterogeneous energetic material,” Ph.D. Thesis, Dept. of Mechanical Engineering, Univ. of Calif., San Diego (1999).

KEYWORDS: meso-scale, structural energetics, heterogeneous materials, interfacial mechanics, chemical reaction models

  • TPOC-1: Martin Schmidt
  • Phone: 850-883-2686
  • Email: martin.schmidt@us.af.mil
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