Elastic properties of carbon nanotube bundle based polymer composite

Abstract

Carbon nanotubes (CNTs) demonstrate unusually high stiffness, strength and resilience, and may become an ideal reinforcing material for nano-composites. CNTs have a propensity to aggregate to bundle or wrap together due to high surface energy and surface area. Therefore, manipulating single CNT or dispersing bundle CNTs is very difficult, and this is the bottleneck for their potential commercial applications. Evaluating the effective material properties of such CNT bundle based polymer composite is very important .at present. In the present research work, a suitable finite element model is developed to investigate the effects of bundle diameter, bundle length and interfacial bonding (i.e. crosslink) between the CNT-CNT and CNT-matrix on the elastic properties cif CNT bundle based polymer composites, using representative volume elements. CNT bundle consisted of four single walled nanotubes is considered here. Diameter of the CNT bundle is varied by varying the diameter of the constituent CNTs of the bundle. Regarding the length ofthe CNT bundle, both short and long bundles are considered. Short bundle remains within the matrix (i.e. bundle. length is smaller than the matrix length) whereas long bundle remains through the length of the matrix. Interface stiffness for the nonbonded van der Waals interaction is determined from the nonlinear cohesive law. The cross-links effect IS incorporated in this research by introducing interface with different stiffness between the CNT-CNT within the bundle and between the CNT and the polymer matrix. For all cases, volume fraction of the CNTs is considered 5%. Then a suitable analytical formula is developed for calculating elastic properties of the equivalent solid fiber as a substitute of the CNT bundle. FEM software is used to determine the elastic properties of the CNT bundle based composites. FEM results of the composites considering the CNT bundle as it is and considering the CNT bundle as an equivalent solid fiber are compared. Present investigation demonstrates that the elastic properties of the CNT bundle based polymer composite are significantly affected by the morphology of the CNT bundle.