Enhanced mechanical properties of single-walled carbon nanotubes due to chemical functionalization

SIMULATION OF THE ELASTIC PROPERTIES OF REINFORCED KEVLAR-GRAPHENE COMPOSITES

The compressive strength of unidirectional fiber composites in the form of Kevlar yarn with a thin outer layer of graphene was investigated and modeled. Such fiber structure may be fabricated by using a strong chemical bond between Kevlar yarn and graphene sheets. Chemical functionalization of graphene and Kevlar may be achieved by modification of appropriate surface-bound functional (e.g., carboxylic acid) groups on their surfaces. In this report we studied elastic response to unidirectional in-plane applied load with load peaks along the diameter. The 2D linear elasticity model predicts that significant strengthening occurs when graphene outer layer radius is about 4% of kevlar yarn radius. The polymer chains of Kevlar are linked into locally planar structure by hydrogen bonds across the chains, with transversal strength considerably weaker than longitudinal one. This suggests that introducing outer enveloping layer of graphene, linked to polymer chains by strong chemical bonds may significantly strengthen Kevlar fiber with respect to transversal deformations.

Molecular mechanics modeling of deformation and failure of super carbon nanotube networks

A generalized molecular structure mechanics (MSM) model is proposed to investigate the deformation and failure behaviors of super carbon nanotubes (SCNTs) within the quasi-static approximation. The failure mechanism of the SCNTs with Y- and X-type junctions was examined by combining a failure criterion for the breakage of the carbon-carbon bonds in the CNT networks. The carbon-carbon bonds are modeled as elastic bars with equivalent stiffness and break as their elongation ratio reaches only 19%, which means that the broken carbon-carbon bonds are ineffective in terms of the Morse potential function. It is shown that the MSM method, combined with the failure criterion of the carbon-carbon bonds, is a powerful approach to simulate the deformation and failure of both Y junctions and X junctions with different chiralities and sizes. The deformation and failure modes of these junctions which involve rotation, bending and stretching of the CNT arms are predicted using the present model and the effects of various parameters of the junctions on their mechanical behaviors are discussed.