Atomistic simulations on multilayer graphene reinforced epoxy composites
01 Aug 2012-Composites Part A-applied Science and Manufacturing (Elsevier)-Vol. 43, Iss: 8, pp 1293-1300
TL;DR: In this article, the authors use molecular dynamics simulations to characterize multilayer graphene reinforced epoxy composites and characterize the in situ curing process of the resin and the thermo-mechanical response of the composites.
Abstract: We use molecular dynamics simulations to characterize multilayer graphene reinforced epoxy composites. We focus on two configurations, one where the graphene layers are parallel to polymer/graphene interface and a perpendicular case, and characterize the in situ curing process of the resin and the thermo-mechanical response of the composites. The yield stress of the composites under uniaxial loading normal to the interface is in all cases larger than that of the bulk polymer even after the constraint of the reinforcement to transverse relaxation is taken into account. While both the parallel and normal configurations have very similar strengths, the parallel case exhibits cohesive yield with strain localization and nano-void formation within the bulk polymer while the case with graphene sheets oriented normal to the interface exhibit interfacial debonding. These two mechanisms lead to different post yield behavior and provide key insight for the development of predictive models of carbon fiber polymer composites.
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TL;DR: In this article, a hierarchical multiscale modeling approach using molecular dynamics (MD) and micromechanical modeling is proposed to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance.
188 citations
TL;DR: In this article, the application of molecular dynamics simulations on mechanical and tribological properties of polymer composites reinforced by carbon nanotubes and graphene sheet as reinforcements is reviewed. And the capabilities of such simulations on exploring inherent mechanisms on improved tribological and mechanical properties of polymeric composites from atomic views are discussed.
Abstract: This paper reviews the application of molecular dynamics simulations on mechanical and tribological properties of polymer composites reinforced by carbon nanotubes and graphene sheet as reinforcements. A variety of simulation studies on modelling, calculation and analysis on enhanced elastic, tensile, fracture properties of carbon nanotubes and graphene sheet/polymer composites are introduced and reviewed. The capabilities of molecular dynamics simulations on exploring inherent mechanisms on improved tribological properties of carbon nanotubes and graphene sheet/polymer composites from atomic views are particularly discussed. Different methods of surface modifications of the two nano reinforcements on further enhancing the strength of polymer composites are summarized. Summary and recommendations for potential researches are also provided. This review is intended to provide a state-of-the-art and better understanding on applications of carbon nanotubes and graphene sheet for enhancing mechanical and tribological properties of polymer composites by molecular dynamics simulations, and inspire future efforts in this area.
146 citations
TL;DR: This approach paves the way for computational screening processes to design, test, and rapidly identify viable surface modifications in silico, which would enable rapid systematic progress in optimizing the match between the carbon fiber treatment and the desired thermoset polymer matrix.
Abstract: Carbon-fiber reinforced composites are ideal light-weighting candidates to replace traditional engineering materials. The mechanical performance of these composites results from a complex interplay of influences operating over several length and time scales. The mechanical performance may therefore be limited by many factors, one of which being the modest interfacial adhesion between the carbon fiber and the polymer. Chemical modification of the fiber, via surface grafting of molecules, is one possible strategy to enhance interactions across the fiber–polymer interface. To achieve systematic improvements in these modified materials, the ability to manipulate and monitor the molecular structure of the polymer interphase and the surface grafted molecules in the composite is essential, but challenging to accomplish from a purely experimental perspective. Alternatively, molecular simulations can bridge this knowledge gap by providing molecular-scale insights into the optimal design of these surface-grafted mo...
110 citations
TL;DR: In this paper, the effect of crosslink density on the conditions of the interface region in graphite/epoxy composites was investigated and it was determined that a surface region exists in the epoxy in which the mass density is different than that of the bulk mass density.
95 citations
Cites methods from "Atomistic simulations on multilayer..."
...[17] used MD simulations to observe the interface of a crosslinked thermoset polymer in the presence of a graphite surface....
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TL;DR: In this article, different types of interatomic potentials can be used for the modeling of graphene, hexagonal boron nitride (h-BN) and corresponding nanocomposites, and further elaborates on developments and challenges associated with the classical mechanics-based approach along with synergic effects of these nano reinforcements on host polymer matrix.
Abstract: Due to their exceptional properties, graphene and hexagonal boron nitride (h-BN) nanofillers are emerging as potential candidates for reinforcing the polymer-based nanocomposites. Graphene and h-BN have comparable mechanical and thermal properties, whereas due to high band gap in h-BN (~5 eV), have contrasting electrical conductivities. Atomistic modeling techniques are viable alternatives to the costly and time-consuming experimental techniques, and are accurate enough to predict the mechanical properties, fracture toughness, and thermal conductivities of graphene and h-BN-based nanocomposites. Success of any atomistic model entirely depends on the type of interatomic potential used in simulations. This review article encompasses different types of interatomic potentials that can be used for the modeling of graphene, h-BN, and corresponding nanocomposites, and further elaborates on developments and challenges associated with the classical mechanics-based approach along with synergic effects of these nano reinforcements on host polymer matrix.
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93 citations
References
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TL;DR: Graphene is established as the strongest material ever measured, and atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.
Abstract: We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.
18,008 citations
"Atomistic simulations on multilayer..." refers background in this paper
...The in-plane tensile strength of MLG is in the 100–130 GPa range [25] and its out-of-plane tensile strength between 1 and 5 GPa [26]....
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TL;DR: In this paper, a new Lagrangian formulation is introduced to make molecular dynamics (MD) calculations on systems under the most general externally applied, conditions of stress, which is well suited to the study of structural transformations in solids under external stress and at finite temperature.
Abstract: A new Lagrangian formulation is introduced. It can be used to make molecular dynamics (MD) calculations on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamical equations given by this Lagrangian. This new MD technique is well suited to the study of structural transformations in solids under external stress and at finite temperature. As an example of the use of this technique we show how a single crystal of Ni behaves under uniform uniaxial compressive and tensile loads. This work confirms some of the results of static (i.e., zero temperature) calculations reported in the literature. We also show that some results regarding the stress‐strain relation obtained by static calculations are invalid at finite temperature. We find that, under compressive loading, our model of Ni shows a bifurcation in its stress‐strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. It is suggested that such a transformation could perhaps be observed experimentally under extreme conditions of shock.
13,937 citations
Additional excerpts
...LAMMPS uses a Holian et al. [27] thermostat and Parrinello–Rahman [28] barostat....
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...[27] thermostat and Parrinello–Rahman [28] barostat....
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TL;DR: The DREIDING force field as discussed by the authors uses general force constants and geometry parameters based on simple hybridization considerations rather than individual force constants or geometric parameters that depend on the particular combination of atoms involved in the bond, angle, or torsion terms.
Abstract: We report the parameters for a new generic force field, DREIDING, that we find useful for predicting structures and dynamics of organic, biological, and main-group inorganic molecules. The philosophy in DREIDING is to use general force constants and geometry parameters based on simple hybridization considerations rather than individual force constants and geometric parameters that depend on the particular combination of atoms involved in the bond, angle, or torsion terms. Thus all bond distances are derived from atomic radii, and there is only one force constant each for bonds, angles, and inversions and only six different values for torsional barriers. Parameters are defined for all possible combinations of atoms and new atoms can be added to the force field rather simply. This paper reports the parameters for the "nonmetallic" main-group elements (B, C, N, 0, F columns for the C, Si, Ge, and Sn rows) plus H and a few metals (Na, Ca, Zn, Fe). The accuracy of the DREIDING force field is tested by comparing with (i) 76 accurately determined crystal structures of organic compounds involving H, C, N, 0, F, P, S, CI, and Br, (ii) rotational barriers of a number of molecules, and (iii) relative conformational energies and barriers of a number of molecules. We find excellent results for these systems.
5,380 citations
"Atomistic simulations on multilayer..." refers methods in this paper
...They were then equilibrated using an isothermal, isobaric (NPT) MD simulation at one atmospheric pressure for 10 ps using the Dreiding force field [14]....
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...The general Dreiding force field [14] with harmonic form of potentials is employed in all simulations....
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TL;DR: In this paper, a general all-atom force field for atomistic simulation of common organic molecules, inorganic small molecules, and polymers was developed using state-of-the-art ab initio and empirical parametrization techniques.
Abstract: A general all-atom force field for atomistic simulation of common organic molecules, inorganic small molecules, and polymers was developed using state-of-the-art ab initio and empirical parametrization techniques. The valence parameters and atomic partial charges were derived by fitting to ab initio data, and the van der Waals (vdW) parameters were derived by conducting MD simulations of molecular liquids and fitting the simulated cohesive energies and equilibrium densities to experimental data. The combined parametrization procedure significantly improves the quality of a general force field. Validation studies based on large number of isolated molecules, molecular liquids and molecular crystals, representing 28 molecular classes, show that the present force field enables accurate and simultaneous prediction of structural, conformational, vibrational, and thermophysical properties for a broad range of molecules in isolation and in condensed phases. Detailed results of the parametrization and validation f...
4,722 citations
"Atomistic simulations on multilayer..." refers methods in this paper
...The COMPASS force field [20] including partial charges and group-based cut-offs [21] for non-bonded interactions was used in the cell construction and subsequent simulations....
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TL;DR: In this article, a force field capable of quantitatively describing the gas, liquid and crystal phases of alcohols, ethers and polyethers is described, with an accuracy of 1% to 2% over extended ranges of at least 200K in temperature and 180MPa in pressure.
Abstract: Parametrization of a force field capable of quantitatively describing the gas, liquid and crystal phases of alcohols, ethers and polyethers is described. Two applications are reported, the first employing atomistic simulations to study PVT (pressure, volume, temperature) and cohesive properties of oligomeric poly(ethylene oxide) (PEO) and related small-molecule liquids, and the second to study the extent of ring formation in polymerization of poly(ethylene glycols) (PEGs) and hexamethylene diisocyanate (HDI). The atomistic simulations, focusing extensively on liquids and amorphous poly(ethylene oxides), demonstrate the ability to predict densities with an accuracy of 1%–2% over extended ranges of at least 200K in temperature and 180MPa in pressure. Densities of related small-molecule liquids, dimethyl and diethyl ether and ethanol at or close to saturation pressure are also well reproduced to temperatures close to the critical temperature. Densities calculated for methoxy-terminated oligomers are used to predict the density of melt and amorphous high-molar-mass PEO with an accuracy of better than 1%. Similarly, solubility parameters have been calculated as a function of chain length for poly(ethylene glycol) oligomers and used effectively to obtain estimates of the solubility parameter of high-molar-mass material. Additionally, crystal structures can also be well predicted. For the polymerization studies the Monte Carlo network simulation method was modified to mimic diffusion of reactants during the polymerization. Application to the PEG/HDI ‘linear’ polymerization system, using chain configurations generated with the atomistic force field, reveals a major improvement in the ability of the method to predict the extent of ring formation without adjustable parameters for polymerization conditions ranging from the bulk to highly dilute reaction conditions. ©1997 SCI
451 citations
"Atomistic simulations on multilayer..." refers methods in this paper
...This dendrimer-based approach with the COMPASS force field has been extensively validated [18,19]....
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