The gr�neisen coefficient for UPV-1 pyrolytic carbon

Stepovik, A. P.

doi:10.1007/bf00864291

Cited by 2 publications

(2 citation statements)

References 7 publications

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“…We verified that the cell is sufficiently large to avoid finite-size effect in the computation of the variables of interests. The range of temperatures explored lies between 400 K and 4000 K (the latter slightly below the expected melting/sublimation point of graphite [28,29] in very good agreement to measures reported in different experimental works [36][37][38]. Results from continuum FEM shock simulations are included in Figure 6 where we also report a magnification of the velocity and pressure Hugoniots of Figure 2.a-b in the range u p < 2 km/s.…”

Section: Equilibrium Thermodynamics Simulations and Fem Solution Of Tsupporting

confidence: 84%

Atomistic modelling of the hypervelocity dynamics of shock-compressed graphite and impacted graphene armours

Signetti

Kang

Pugno

et al. 2019

Computational Materials Science

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We present a molecular dynamics (MD) simulation study on the hypervelocity dynamics of shock compressed graphite-up to hundreds of gigapascals-and impacted multilayer graphene armours by employing the AIREBO-M potential. The Morse-type non-singular intermolecular interaction allows the usage of relatively large integration timesteps for simulating materials' response at such high strain-rate. The MD simulation results are in good agreement with the shock Hugoniot curves and with graphite-to-diamond transition obtained from both density functional theory (DFT) and experiments available in literature. We then show that thermodynamic properties of graphite from MD calculations can be used as input for a reliable equation of state to be employed in continuum simulations. Finally, we find that the size-scaling of the hypervelocity impact properties of graphene armours matches well with the DFT results and theoretical predictions of earlier studies. Our results open a concrete possibility towards accurate and fast multiscale simulation from atomistic to continuum level of shock propagation, shock-induced phase transformation, and dynamic fracture in large or hierarchical carbon systems, such as graphene-based foams and nanocomposites.

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Section: Equilibrium Thermodynamics Simulations and Fem Solution Of Tsupporting

confidence: 84%

Atomistic modelling of the hypervelocity dynamics of shock-compressed graphite and impacted graphene armours

Signetti

Kang

Pugno

et al. 2019

Computational Materials Science

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“…The Grüneisen coefficient of pyrocarbon was measured as follows [10]. Two samples 60 mm in diameter and 10 mm thick were prepared; the samples had different orientation of planes with respect to the direction of carbon deposition: perpendicular and parallel to the deposition plane.…”

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confidence: 99%

Measurement of the Gruneisen Coefficient of Some Anisotropic Carbon Materials

Stepovik

2005

J Appl Mech Tech Phys

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Results of measurement of the Grüneisen coefficient of two anisotropic materials (4KMS carboncarbon composite and UPV-1 pyrolytic carbon) are presented. The values of the Grüneisen coefficient are calculated on the basis of the measured amplitude of mechanical stresses arising in the material with absorption of electron-beam energy. The results for the 4KMS composite include not only a negative value of the Grüneisen coefficient in the range of electron energy density of several tens of joules per square centimeter but also its anomalously low value as compared to other materials. Significant decay of the stress wave propagating over this material is noted. The Grüneisen coefficient of the UPV-1 sample varies depending on the sample orientation.Composites are rather promising and interesting materials. A particular group of composites consists of carbon-carbon composites, i.e., materials obtained from carbon fibers with the matrix being filled by carbon.Calculation of thermoelastic stresses upon pulsed heating by radiation in such materials is rather complicated for a number of reasons: possible nonuniform heating over the depth of the material, complicated pattern of stress waves arising in such an inhomogeneous material, transformation of these stresses propagating in the depth of the composite, etc. Composite materials under pulsed radiation by an electron beam with duration of tens of nanoseconds or by laser radiation with duration of several nanoseconds were considered in several papers (see, e.g., [1,2]). Materials with a two-dimensional structure were studied, which made it possible to construct a phenomenological models that could involve Grüneisen coefficients directly measured in experiments [1][2][3].In the present work, we made an attempt to consider the behavior of a material with three-dimensional anisotropy (4KMS carbon-carbon composite) under pulsed heating and to compare the results obtained with data for a material based on the same substance but with a typical two-dimensional structure (pyrolytic carbon and UPV-1 pyrocarbon). Pyrocarbon is obtained by means of methane deposition onto a hot graphite surface; hence, its structure is actually two-dimensional. Figure 1 shows a typical form of the surface of a sample cut out from a composite billet. The untreated surface of a pyrocarbon plate on the side of methane deposition is shown in Fig. 2.We chose the Grüneisen coefficient as a parameter characterizing the material behavior. The energy input was performed by a pulsed electron beam with duration of several tens of nanoseconds. The energy of electrons absorbed by the material is finally converted to the thermal energy of the substance lattice and generates thermoelastic stresses in the material. The process of energy transfer to lattice atoms is normally rather fast; if the electron pulse is short as compared to the relaxation time of the material, the profile of the arising waves of thermoelastic stresses is close to the profile of energy release in the material [4]. An exception is materials w...

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The gr�neisen coefficient for UPV-1 pyrolytic carbon

Cited by 2 publications

References 7 publications

Atomistic modelling of the hypervelocity dynamics of shock-compressed graphite and impacted graphene armours

Atomistic modelling of the hypervelocity dynamics of shock-compressed graphite and impacted graphene armours

Measurement of the Gruneisen Coefficient of Some Anisotropic Carbon Materials

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