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.
