Computational study of uniaxial deformations in silica aerogel using a coarse-grained model

Carlos A. Ferreiro-Rangel, Lev D. Gelb

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Simulations of a flexible coarse-grained model are used to study silica aerogels. This model, introduced in a previous study (J. Phys. Chem. C 2007, 111, 15792), consists of spherical particles which interact through weak nonbonded forces and strong interparticle bonds that may form and break during the simulations. Small-deformation simulations are used to determine the elastic moduli of a wide range of material models, and large-deformation simulations are used to probe structural evolution and plastic deformation. Uniaxial deformation at constant transverse pressure is simulated using two methods: a hybrid Monte Carlo approach combining molecular dynamics for the motion of individual particles and stochastic moves for transverse stress equilibration, and isothermal molecular dynamics simulations at fixed Poisson ratio. Reasonable agreement on elastic moduli is obtained except at very low densities. The model aerogels exhibit Poisson ratios between 0.17 and 0.24, with higher-density gels clustered around 0.20, and Young's moduli that vary with aerogel density according to a power-law dependence with an exponent near 3.0. These results are in agreement with reported experimental values. The models are shown to satisfy the expected homogeneous isotropic linear-elastic relationship between bulk and Young's moduli at higher densities, but there are systematic deviations at the lowest densities. Simulations of large compressive and tensile strains indicate that these materials display a ductile-to-brittle transition as the density is increased, and that the tensile strength varies with density according to a power law, with an exponent in reasonable agreement with experiment. Auxetic behavior is observed at large tensile strains in some models. Finally, at maximum tensile stress very few broken bonds are found in the materials, in accord with the theory that only a small fraction of the material structure is actually load-bearing.

LanguageEnglish
Pages8640-8650
Number of pages11
JournalJournal of Physical Chemistry B
Volume119
Issue number27
Early online date25 Jun 2015
DOIs
Publication statusPublished - 9 Jul 2015

Fingerprint

Aerogels
aerogels
Silicon Dioxide
Silica
silicon dioxide
Elastic moduli
modulus of elasticity
Tensile strain
Poisson ratio
simulation
Molecular dynamics
Bearings (structural)
exponents
molecular dynamics
Tensile stress
tensile stress
bulk modulus
Plastic deformation
tensile strength
Tensile strength

Keywords

  • silica aerogel
  • spherical particles
  • material models
  • molecular dynamics

Cite this

Ferreiro-Rangel, Carlos A. ; Gelb, Lev D. / Computational study of uniaxial deformations in silica aerogel using a coarse-grained model. In: Journal of Physical Chemistry B . 2015 ; Vol. 119, No. 27. pp. 8640-8650.
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Computational study of uniaxial deformations in silica aerogel using a coarse-grained model. / Ferreiro-Rangel, Carlos A.; Gelb, Lev D.

In: Journal of Physical Chemistry B , Vol. 119, No. 27, 09.07.2015, p. 8640-8650.

Research output: Contribution to journalArticle

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