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Mesoscale simulation of shocked poly-(4-methyl-1-pentene) (PMP) foams

AIP Conference Proceedings

Haill, Thomas A.; Mattsson, Thomas M.; Root, Seth R.; Schroen, D.G.; Flicker, Dawn G.

Hydrocarbon foams are commonly used in high energy-density physics (HEDP) applications, for example as tamper and ablation materials for dynamic materials or inertial confinement fusion (ICF) experiments, and as such are subject to shock compression from tens to hundreds of GPa. Modeling of macro-molecular materials like hydrocarbon foams is challenging due to the heterogeneous character of the polymers and the complexity of voids and large-scale structure. Under shock conditions, these factors contribute to a relatively larger uncertainty of the post-shock state compared to that encountered for homogenous materials; therefore a quantitative understanding of foams under strong dynamic compression is sought. We use Sandia's ALEGRA-MHD code to simulate 3D mesoscale models of poly-(4-methyl-1-pentene) (PMP) foams. We devise models of the initial polymer-void structure of the foam and analyze the statistical properties of the initial and shocked states. We compare the simulations to multi-Mbar shock experiments conducted on Sandia's Z machine at various initial foam densities and flyer impact velocities. Scatter in the experimental data may be a consequence of the initial foam inhomogeneity. We compare the statistical properties of the simulations with the scatter in the experimental data. © 2012 American Institute of Physics.

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TYPE Conference YEAR 2012
ScopusOSTI

Density functional theory (DFT) simulations of polyethylene: Principal hugoniot, specific heats, compression and release isentropes

AIP Conference Proceedings

Cochrane, Kyle R.; Desjarlais, Michael P.; Mattsson, Thomas M.

An accurate equation of state (EOS) for polyethylene is required in order to model high energy density experiments for CH2 densities above 1 g/cc, temperatures above 1 eV, and pressures above 1 Mbar. Density Functional Theory (DFT) based molecular dynamics has been established as a method capable of yielding high fidelity results for many materials at a wide range of pressures and temperatures and has recently been applied to complex polymers such as polyethylene [1]. Using high density polyethylene as the reference state, we compute the principal Hugoniot to 350 GPa, compression isentrope, and several release isentropes from states on the principal Hugoniot. We also calculate the specific heat and the dissociation along the Hugoniot. Our simulation results are validated by comparing to experimental data [2, 3] and then used to construct a wide range EOS. © 2012 American Institute of Physics.

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TYPE Conference YEAR 2012
ScopusOSTI
Results 101–125 of 178
Results 101–125 of 178