Theoretical study of the porosity effects on the shock response of graphitic materials

Nicolas Pineau,Jean-Bernard Maillet,David Hébert,Laurent Soulard,Emeric Bourasseau,E Cadoni

doi:10.1051/epjconf/20159404037

Nicolas Pineau, Jean-Bernard Maillet + Show 4 more

Open Access

https://doi.org/10.1051/epjconf/20159404037

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Abstract

In this paper we present a theoretical study of the shock compression of porous graphite by means of combined Monte Carlo and molecular dynamics simulations using the LCBOPII potential. The results show that the Hugoniostat methods can be used with “pole” properties calculated from porous models to reproduce the experimental Hugoniot of pure graphite and diamond with good accuracy. The computed shock temperatures show a sharp increase for weak shocks which we analyze as the heating associated with the closure of the initial porosity. After this initial phase, the temperature increases with shock intensity at a rate comparable to monocrystalline graphite and diamond. These simulations data can be exploited in view to build a full equation of state for use in hydrodynamic simulations.

Highlights

The responses of carbon materials under high pressure and temperature constraints have motivated a large number of experimental and theoretical studies in the academic and applied physics fields [1,2,3,4,5,6,7,8,9]
Experimentally shock-compressed graphite can span porosity rates ranging up to more than 20%, yielding graphite to diamond (G/D) transition pressures from 18 to 45 GPa. These values lie substantially above the estimated G/D coexistence line, which signs a possible metastability of shocked graphite in the diamondpredominant regime
In the Monte Carlo (MC)-SCA framework, the complex structure of the polycrystalline samples was accounted for by using a pole energy estimated from several model of porous structures, corresponding the variety of porosity types in granular materials

Summary

Introduction

The responses of carbon materials under high pressure and temperature constraints have motivated a large number of experimental and theoretical studies in the academic and applied physics fields [1,2,3,4,5,6,7,8,9]. Building accurate equations of state (EOS) remains a very challenging problem due to a lack of reliable experimental data on the thermal effects associated to its diverse forms and transformations: temperature measurements can be difficult under extreme, highly dynamic constraints. This difficulty increases in the case of porous systems due to the differences between the initial samples used in the reference experiments. We compare our Hugoniot data to experimental results and discuss the role of the sample porosity on the resulting equation of state

Numerical setup

Results and discussion

Conclusion