The reinforcing nanostructures can be made up of nanoparticles, nanosheets or nanofibres such as carbon nanotubes (CNTs) and graphene nanosheets. To investigate the reinforce mechanism, the changes in mechanical behavior of CNT reinforced Polyurethane (PU) matrix with various chirality was studied using molecular dynamics (MD) method in current work. We used the DREIDING and Tersoff force-fields for simulation of the PU and CNT samples, respectively. To report the mechanical properties of pristine PU matrix and reinforced PU/CNT structure, some physical parameters such as interaction energy between polymer chains and nanotube atoms, ultimate strength, and Young’s modulus are calculated. MD outputs indicated inserting CNT with zigzag edge into pristine matrix enlarged the Young’s modulus by 17.10% and the ultimate strength by 25.69%. These results indicated the promising effect of CNT-based nanostructures on the mechanical properties of PU matrix.

Molecular dynamics (MD) simulation has been applied to study of pull-out of Halloysite nanotubes (HNTs) from a polyurethane (PU) matrix. First, the Machine learning (ML) particle swarm optimization (PSO) method was used to obtain force field parameters for MD from data of density functional theory (DFT) calculations. The current study shows the possibility of using a PSO technique to modify the force field with DFT data with less than 5 kcal/mol discrepancy. Second, we considered the influence of atomic interface on pulling out of HNT from PU. Energy variation has been proposed as the cohesion strength between matrix and nanoparticle. In addition, the best Lennard Jones parameters in the MD simulation make good agreement with an experimental sample stress-strain response.

Molecular dynamics simulation was applied to study the irreversible strain through loading and unloading cyclic tests of polyurethane (PU) reinforced with halloysite nanotube (HNT). The influences of the stretching cycle rate, different temperatures, the volume of halloysite nanotube and the density rate of the hard and soft domain of PU were studied on the permanent set. The results illustrate that the residual strain was increasing when the stretching loading is increasing, for example, with increasing strain load to 250% the residual strain increased to 55%. In contrast, the increasing volume fraction of HNT and hard part content of PU lead to lower residual strain. The recovery of the permanent set is achievable by increasing temperature from 1 K to 200 K residual strain is decreased to 52%. An Ogden constitutive and the theory of pseudo-elasticity were adopted to simulate this composite in the ABAQUS software. This model has proposed a reasonable prediction of plastic deformation.

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In this study, we simulated the rolling mechanism of Halloysite by molecular dynamics (MD) under different conditions. We have illustrated that the transformation from slab Halloysite to scroll shape depends on the initial geometry, dimension and proper selection of the interatomic potential. Also, the molecular simulation was conducted to determine the mechanical properties of Halloysite under different conditions. The results show that the Elastic modulus of the armchair Nano scroll was higher than the zigzag with similar dimensions and that Young's modulus of both arrangements decreases with increased radius. Moreover, with an increasing radius (>20 Å), Young's modulus of a Halloysite nano-scroll approaches that of the Halloysite slab configuration. Finally, the tensile strain of a Halloysite nanosheet was 0.08±0.04. The result of this study is a great help for understanding Halloysite, which can be used for designing nanocomposites.