Pull-out simulations of a capped carbon nanotube in carbon nanotube-reinforced nanocomposites

Abstract

Systematic atomic simulations based on molecular mechanics were conducted to investigate the pull-out behavior of a capped carbon nanotube (CNT) in CNT-reinforced nanocomposites. Two common cases were studied: the pull-out of a complete CNT from a polymer matrix in a CNT/polymer nanocomposite and the pull-out of the broken outer walls of a CNT from the intact inner walls (i.e., the sword-in-sheath mode) in a CNT/alumina nanocomposite. By analyzing the obtained relationship between the energy increment (i.e., the difference in the potential energy between two consecutive pull-out steps) and the pull-out displacement, a set of simple empirical formulas based on the nanotube diameter was developed to predict the corresponding pull-out force. The predictions from these formulas are quite consistent with the experimental results. Moreover, the much higher pull-out force for a capped CNT than that of the corresponding open-ended CNT implies a significant contribution from the CNT cap to the interfacial properties of the CNT-reinforced nanocomposites. This finding provides a valuable insight for designing nanocomposites with desirable mechanical properties. V

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“…However, Li and his co-workers [20] found that the interfacial shear stress (ISS) between CNT and polymer matrix distributes at each end of the embedded CNT within the range of 1nm during the pull-out process. By molecular mechanics simulation, they also found that a capped CNT presents a higher pull-out force than that of the corresponding open-ended CNT [21]. As the MD simulation is mostly limited to systems with several nanometers and tens of particles [22,23], a large proportion of atoms, whether CNT atoms or polymer ones, have to be located in the region where the "end effect" is intense.…”

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