Bio-Inspired Carbon Nanotube-Polymer Composite Yarns with Hydrogen Bond-Mediated Lateral Interactions.
ABSTRACT Polymer composite yarns containing a high loading of double-walled carbon nanotubes (DWNTs) have been developed in which the inherent acrylate-based organic coating on the surface of the DWNT bundles interacts strongly with poly(vinyl alcohol) (PVA) through an extensive hydrogen-bond network. This design takes advantage of a toughening mechanism seen in spider silk and collagen, which contain an abundance of hydrogen bonds that can break and reform, allowing for large deformation while maintaining structural stability. Similar to that observed in natural materials, unfolding of the polymeric matrix at large deformations increases ductility without sacrificing stiffness. As the PVA content in the composite increases, the stiffness and energy to failure of the composite also increases up to an optimal point, beyond which mechanical performance in tension decreases. Molecular dynamics (MD) simulations confirm this trend, showing the dominance of nonproductive hydrogen bonding between PVA molecules at high PVA contents, which lubricates the interface between DWNTs.
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ABSTRACT: Understanding of atomic interactions between constituents is critical to the design of high-performance nanocomposites. Here, we report an experimental-computational approach to investigate the adhesion energy between as-produced arc discharge multiwalled carbon nanotubes (MWCNTs) and graphene. An in situ scanning electron microscope (SEM) experiment is used to peel MWCNTs from graphene grown on copper foils. The force during peeling is obtained by monitoring the deflection of a cantilever. Finite element and molecular mechanics simulations are performed to assist the data analysis and results interpretation. A finite element analysis of the experimental configuration is employed to confirm the applicability of Kendall's peeling model to obtain the adhesion energy. Molecular mechanics simulations are used to estimate the effective contact width at the MWCNT-graphene interface. The measured surface energy is γ = 0.20 ± 0.09 J-m(-2) or γ = 0.36 ± 0.16 J-m(-2), depending on the assumed conformation of the tube cross section during peeling. The scatter in the data is believed to result from an amorphous carbon coating on the MWCNTs, observed using transmission electron microscopy (TEM), and the surface roughness of graphene as characterized by atomic force microscopy (AFM).ACS Nano 12/2013; 8(1). · 12.03 Impact Factor
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ABSTRACT: Functionalized graphene oxide-reinforced poly(vinyl alcohol) hybrid composites were prepared by using the sol–gel method. This method not only provided a “green” strategy for fabricating the graphene oxide-based composites, but also realized the covalent functionalization of graphene oxide nanosheets with polymer matrix. The morphology, thermal, fire resistance and mechanical properties of the f-GNS/poly(vinyl alcohol) hybrid composites were systematically studied. The transmission electron microscopy analyses demonstrated that f-GNS was homogeneously dispersed in the poly(vinyl alcohol) matrix. Combining with a series of analyses and characterizations, it was observed that the functionalization of graphene oxide with conjugated organosilanes was favorable for improving mechanical, thermal properties and flame retardance of the composites, which was mainly attributed to the homogeneous dispersion of functionalized graphene oxide in the polymer matrix and strong interfacial interactions between the two components.Composites Science and Technology 10/2014; 102:51–58. · 3.63 Impact Factor
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ABSTRACT: The recently developed distinct element method for mesoscale modeling of carbon nanotubes is extended to account for energy dissipation and then applied to character-ize the constitutive behavior of crystalline carbon nanotube bundles subjected to simple tension and to simple shear loadings. It is shown that if these structures are sufficiently long and thick, then they become representative volume elements. The predicted initial stiffness and strength of the representative volumes are in agreement with reported ex-perimental data. The simulations demonstrate that energy dissipation plays a central role in the mechanical response and deformation kinematics of carbon nanotube bundles.Journal of Applied Mechanics 06/2014; · 1.40 Impact Factor