The stress–strain behavior of polymer–nanotube composites from molecular dynamics simulation (original) (raw)
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The Stress-strain Behavior of Polymer-nanotube Composites from Molecular Dynamics Simulations
2002
Stress–strain curves of polymer–carbon,nanotube,composites,generated,from,molecular,dynamics,simulations,of a single-walled carbon,nanotube,embedded,in polyethylene,are presented. A comparison,is made,between,the response,to mechanical,loading of a composite with a long, continuous nanotube (replicated via periodic boundary conditions) and the response of a composite with a short, discontinuous nanotube. Both composites are mechanically loaded in the direction of, and transverse to, the nanotube axis. The long-nanotube,composite,shows,an increase in the stiffness
International Journal of Molecular Sciences
The use of carbon nanotubes to improve the mechanical properties of polymers is one of the promising directions in materials science. The addition of single-walled carbon nanotubes (SWCNTs) to a polymer results in significant improvements in its mechanical, electrical, optical, and structural properties. However, the addition of SWCNTs does not always improve the polymer properties. Also, when a certain content of SWCNTs is exceeded, the mechanical properties of the nanocomposite become worse. This article reports the results of computer simulations for predicting the mechanical properties of polymer/single-walled carbon nanotube nanocomposites. The efficiency of reinforcing polymer composites is considered depending on the concentration of carbon nanotubes in the polymer matrix, their size, and structure. The elastic moduli of the nanocomposites are predicted using computer simulations for unit cell tension (0.1%). General trends in the mechanical properties of composites with poly...
Concepts, Methodologies, Tools, and Applications
In recent years, polymer/carbon nanotube composites have attracted increased attention because the polymer properties have significantly improved. In this paper, a single walled carbon nanotube (SWCNT) is used to reinforce polystyrene matrix. Molecular dynamics (MD) simulations are used to study two periodic systems - a long CNT-reinforced polystyrene composite and amorphous polystyrene matrix itself. The axial and transverse elastic moduli of the amorphous polystyrene matrix and nanocomposites are evaluated using constant-strain energy minimization method. The results from MD simulations are compared with corresponding rule-of-mixture predictions. The simulation results show that CNTs significantly improve the stiffness of polystyrene/CNT composite, especially in the longitudinal direction of the nanotube. Polystyrene posses a strong attractive interaction with the surface of the SWCNT and therefore play an important role in providing effective adhesion. The conventional rule-of-mi...
Carbon nanotubes have caught tremendous attention of the researchers during the last decade due to their excellent mechanical, electrical, optical and thermal properties. The exploitation of these fibers as reinforcing agents in making strong fiber composites has been a primary research topic in the recent investigations on composite materials. Although the theoretical results are rather optimistic, the goal of achieving high strength of the carbon nanotube composites is still not satisfactorily realized. We report here a comparative study of the mechanical properties of single-walled, multi-walled and bundle of single-walled carbon nanotubes. Their mechanical behavior is investigated by molecular dynamics simulation, considering Brenner’s second generation reactive empirical bond order interatomic potential between the carbon atoms making a tube. For a long range interaction, we have defined a weak van der Waals force which acts between different layers of a multi-walled tube or between different tubes of a bundle. Samples of three isolated armchair single-wall carbon nanotubes of different diameters, a multi-wall armchair carbon nanotube and finally a bundle of three armchair single-walled nanotubes of same diameter are taken. Their fracture pattern and buckling behavior are modeled and compared. Significant changes are observed in the mechanical properties of the samples of different types of carbon nanotubes which arise due to the interaction between the shells of a multi-walled tube or the tubes in a bundle.
Mechanical Properties of CNT-Reinforced Polymer Nano-composites: A Molecular Dynamics Study
2016
Understanding the mechanism underlying the behavior of polymer-based nanocomposites requires investigation at the molecular level. In the current study, an atomistic simulation based on molecular dynamics was performed to characterize the mechanical properties of polycarbonate (PC) nanocomposites reinforced with single-walled armchair carbon nanotubes (SWCNT). The stiffness matrix and elastic properties such as Young’s modulus, shear and bulk moduli, and Poisson’s ratio for the pure PC and PC/CNT nanocomposites were estimated using the constant-strain method. In this research, this method was used for the first time to investigate the effects of different parameters, such as the effects of weight fraction and aspect ratio of CNTs on the elastic properties of PC/SWCNT nanocomposites. From the computational results, the elastic moduli of PC/CNT nanocomposites increased with increasing the amount of incorporated CNTs, while their aspect ratio (l/d) also increased. A significant increas...
ISRN Materials Science
The rate-dependent interfacial behavior between a carbon nanotube (CNT) and a polyethylene (PE) matrix is investigated using molecular dynamics (MD) simulations. Various MD simulations were set up to determine the “size” effects on the interfacial properties, such as the molecular weight, or the length of the polymer, the diameter of the CNT, and the simulation model size. The interfacial rate-dependency was probed by applying various relative sliding velocities between the CNT and the polymer. Two quantities, directly obtained from the MD simulations, described the interfacial properties: the critical interfacial shear stress (CISS) and the steady interfacial shear stress (SISS). The simulations show that the SISS was not sensitive to the simulation size. In addition, the CISS was dependent upon the combined factors of the variation in PE stiffness, induced by simulation size changes and the effect of the fixed boundaries of the simulation models. The CISS increases almost linearly...
3D Molecular Dynamics/Finite Element Simulation of Carbon Nanotubes-Reinforced Polymer Composites
Journal of Computational and Theoretical Nanoscience, 2015
A simulation of the mechanical behavior of a carbon nanotubes-reinforced polymeric composite, based on Flory’s statistical segment approach, is presented. The material is modeled at the micro and nano levels. Interactions between molecules are Morse-like potentials, as well as Van der Walls forces. Traditional simulations involve Molecular Dynamics by solving Newton’s equations of motion, Instead, we apply here a finite element approach, involving nonlinear elements to take into account the potential interactions. Amorphous polymer chains are represented by statistical segments, in which several repeating units of a chain are treated as single and independent components. This model allows the simulation at a large scale as compared to those using the unit-atom model or those performed at the atomistic level.
Constitutive Modeling of Nanotube-Reinforced Polymer Composite Systems
2001
In this study, a technique has been proposed for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Since the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties of the SWNT/polymer composites can no longer be determined through traditional micromechanical approaches that are formulated using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalentcontinuum modeling method. The effective fiber retains the local molecular structure and bonding information and serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube sizes and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyethylene composite systems, one with continuous and aligned SWNT and the other with discontinuous and randomly aligned nanotubes.
Constitutive modeling of nanotube–reinforced polymer composites
Composites Science and Technology, 2003
In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalentcontinuum modeling method. The effective fiber serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube shapes, sizes, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/LaRC-SI (with a PmPV interface) composite systems, one with aligned SWNTs and the other with three-dimensionally randomly oriented SWNTs. The Young's modulus and shear modulus have been calculated for the two systems for various nanotube lengths and volume fractions.