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Graphene Foam: Hole-Flake Network for Uniaxial Supercompression and Recovery Behavior
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posted on 2018-11-05, 12:51 authored by Douxing Pan, Chao Wang, Xiaojie WangWe
employed the coarse-grained molecular dynamics simulation method
to systematically study the uniaxial supercompression and recovery
behavior of multiporous graphene foam, in which a mesoscopic three-dimensional
network with hole-graphene flakes was proposed. The network model
not only considers the physical cross-links and interlayer van der
Waals interactions, but also introduces a hole in the flake to approach
the imperfection of pristine graphene and the hierarchical porous
configuration of real foam material. We first recreated a typical
two-stage supercompression stress–strain relationship and the
corresponding time-dependent recovery as well as a U-type nominal
Poisson ratio. Then the recovery unloading at different strains and
multicycle compression–uncompression were both conducted; the
initial elastic moduli in the multicycles were found to be the same,
and a multilevel residual strain was disclosed. Importantly, the residual
strain is not exactly the plastic one, part of which can resurrect
in the subsequent loading–unloading–holding. The mesoscopic
mechanism of viscoelastic and residual deformation for the recovery
can be attributed to the van der Waals repulsion and mechanical interlocking
among the hole-flakes; interestingly, the local tensile stress was
observed in the virial stress distribution. Particularly, an abnormal
turning point in the length-time curve for the mean bead-bond length
was captured during the supercompression. After the point, the length
abnormally increases for different size ratios of the hole to the
flake, which is in line with the mesostructure evolution. The finding
may provide a mesoscopic criterion for the supercompression of graphene
foam related materials.
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Keywords
size ratiosmesoscopic mechanismnetwork modelfoam materialPoisson ratioHole-Flake Networkdynamics simulation methodmulticyclegraphene foamrecovery behaviormesostructure evolutionbead-bond lengthmesoscopic criterionvan der Waals repulsiontime-dependent recoveryUniaxial Supercompressionvirial stress distributionmultiporous graphene foamhole-graphene flakesstrainGraphene Foaminterlayer van der Waals interactionslength-time curveuniaxial supercompressionRecovery Behavior
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