Investigating the Effect of Carbon Nanotube Defects on the Column and Shell Buckling of Carbon Nanotube-Polymer Composites Using Multiscale Modeling

摘要

Carbon nanotube (CNT)-reinforced polymer composites have attracted great attention due to their exceptionally high strength. Their high strength can be affected by the presence of defects in the nanotubes used as reinforcements in practical nanocomposites. In this article, a new three-phase molecular structural mechanics/finite element (MSM/FE) multiscale model is used to study the effect of CNT vacancy defects on the stability of single-wall (SW) CNT-polymer composites. The nanotube is modeled at the atomistic scale using MSM, whereas the interphase layer and polymer matrix are analyzed by the FE method. The nanotube and polymer matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones potential. Here, two of the most commonly used buckling regimes of CNTs, called column and shell buckling, are considered. To study the stability of the nanocomposites, the buckling onset strain is calculated for perfect and defected CNTs in the polymer nanocomposites. The results reveal that the presence of vacancy defects causes a decrease in the axial buckling strain of SWCNT-polymer composites. Meanwhile, this decrease is much more noticeable in the case of the column buckling mode. Also, it is shown that decreasing the CNT diameter causes a reduction in the onset buckling strain of defected nanocomposites. Finally, the role of the interphase layer on the stability behavior of these nanocomposites is discussed. It is concluded that the existence of a more compact layer than the polymer chains coated on the nanotube can enhance drastically the buckling behavior of these nanocomposites (about 35%).