Chirality-Dependent Mechanical Properties of Bundles and Thin Films Composed of Covalently Cross-Linked Carbon Nanotubes

Abstract

The effect of nanotube chirality on the mechanical properties of materials composed of single-walled carbon nanotubes (CNTs) is poorly understood since the interfacial load transfer in such materials is strongly dependent on the intertube interaction and structure of the nanotube network. Here, a combined atomistic-mesoscopic study is performed to reveal the effect of CNT diameter on the deformation mechanisms and mechanical properties of CNT bundles and low-density CNT films with covalent cross-links (CLs). First, the pullout of the central nanotube from bundles composed of seven (5,5), (10,10), (20,20), (17,0), and (26,0) CNTs is studied in molecular dynamics simulations based on the ReaxFF force field. The simulations show that the shear modulus and strength increase with decreasing CNT diameter. The results of atomistic simulations are used to parametrize a mesoscopic model of CLs and to perform mesoscopic simulations of in-plane tension and compression of thin films composed of thousands of cross-linked CNTs. The mechanical properties of CNT films are found to be strongly dependent on CNT diameter. The film modulus increases as the CNT diameter increases, while the tensile strength decreases. The in-plane compression is characterized by collective bending of whole films and order-of-magnitude smaller compressive strengths. The films composed of (5,5) CNTs exhibit the ability for large-strain compression without irreversible changes in the material structure. The stretching rigidity of individual nanotubes and volumetric CL density are identified as the key factors that dominate the effect of CNT chirality on the mechanical properties of CNT films. The film modulus is affected by both CL density and stretching rigidity of CNTs, while the tensile strength is dominated by CL density. The obtained results suggest that the on-demand optimization of the mechanical properties of CNT films can be performed by tuning the nanotube chirality distribution.

Modeling Carbon Nanotube Entanglement Load Transfer: Implications for Lightweight Aerospace Structures

“…This transient bond breaking and reformation phenomenon is similar to what has been reported in other studies of carbon nanotube cross-linking. 46,47 The magnitudes of load transfer of the reactive models are much larger than those of the nonreactive models with a mean load transfer of 1.491 ± 1.095 N/ tex, which is ∼14 times greater than the non-reactive models. The distribution of mean load transfer is shown in Figure 5.…”

Optimization of thermoelectric properties of carbon nanotube veils by defect engineering

“…The gaps are formed due to finite-strain-rate effects, since the maximum deformation speed, corresponding to a quasi-static tension for the considered sample, is expected to be smaller than 10 m s À1 . 61 This relatively high deformation speed is chosen intentionally to mimic in simulations the formation of cracks in the experimental samples of CNT veils. At a strain of 89%, the density in the gaps is about 3 times smaller than that in the central part of the film (Fig.…”

Bisphenol-A–Carbon Nanotube Nanocomposite: Interfacial DFT Prediction and Experimental Strength Testing

“…The multi-walled CNTs and acetone-functionalized CNTs (A-CNTs) have become a highly potent candidate to be used as the filler in composite materials owing to their high aspect ratio, high active surface area, and extraordinary mechanical characteristics. The CNTs have been used for various applications in potent areas such as rubber/polymer/metal composites, − sensing, , biomedical, catalysts, and energy storage and strength. − The nanocomposites with CNT reinforcement yield superior specific properties like high strength-to-weight and high stiffness-to-weight ratios. However, CNTs have strong tendency to form aggregates in solution.…”