https://imechanica.org/files/Thostenson-Li-Chou-05-CST.pdf

Nanocomposites in context

This paper reviews recent studies conducted on carbon nanotube/polymer composites. Carbon nanotubes are promising new materials for blending with polymers with potential to obtain low-weight nanocomposites of extraordinary mechanical, electrical, thermal and multifunctional properties. The size scale, aspect ratio and properties of nanotubes provide advantages in a variety of applications, including electrostatically dissipative materials; advanced materials with combined stiffness, strength and impact for aerospace or sporting goods; composite mirrors; automotive parts that require electrostatic painting and automotive components with enhanced mechanical properties. The various processing methods for producing these nanocomposites are discussed, in particular melt mixing, solution processing and in-situ polymerization. Some key results are summarized, relating to the mechanical, electrical, thermal, optical and surface properties. Finally, the challenges for the future are discussed in terms of processing, characterization, nanotube availability, nanotube tailoring, and the mechanisms governing the behavior of these remarkable nanoscale composites. Polym. Compos. 25:630–645, 2004. © 2004 Society of Plastics Engineers.

Big returns from small fibers: A review of polymer/carbon nanotube composites

The state of research into carbon nanotube/polymer–matrix composites for mechanical reinforcement is critically reviewed with emphasis on recent advances in CNT composite toughness. Particular interest is also given to interfacial bonding of carbon nanotubes to polymer matrices as it applies to stress transfer from the matrix to the CNT. Potential topics of oncoming focus are highlighted.

Carbon nanotube polymer composites

Unperturbed dimensions of stereoregular polymers.- Reinforcement of rubber by carbon black.- Transformations of phenolic antioxidants and the role of their products in the long-term properties of polyolefins.

Properties of polymers

In this work, multiwalled carbon nanotubes were investigated as potential mechanical reinforcement agents in two hosts, polyvinyl alcohol (PVA) and poly(9-vinyl carbazole) (PVK). It was found that, by adding various concentrations of nanotubes, both Young’s modulus and hardness increased by factors of 1.8 and 1.6 at 1 wt % in PVA and 2.8 and 2.0 at 8 wt % in PVK, in reasonable agreement with the Halpin–Tsai theory. Furthermore, the presence of the nanotubes was found to nucleate crystallization of the PVA. This crystal growth is thought to enhance matrix-nanotube stress transfer. In addition, microscopy studies suggest extremely strong interfacial bonding in the PVA-based composite. This is manifested by the fracture of the polymer rather that the polymer-nanotube interface.

/pdf/morphological-and-mechanical-properties-of-carbon-nanotube-3s4njyjqk0.pdf

Morphological and mechanical properties of carbon-nanotube-reinforced semicrystalline and amorphous polymer composites

Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and van der Waals forces for polymer-nanotube interface have been used to investigate thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Addition of carbon nanotubes to polymer matrix is found to significantly increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. The increase has been attributed to the temperature dependent increase of the excluded volume for the polymer chains, and the findings could have implications in the composite processing, coating and painting applications.

/pdf/thermal-expansion-and-diffusion-coefficients-of-carbon-3x4t78q9zb.pdf

Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites

Strain rate and temperature dependence of the tensile strength of single-wall carbon nanotubes has been investigated with molecular dynamics simulations. The tensile failure or yield strain is found to be strongly dependent on the temperature and strain rate. A transition state theory based predictive model is developed for the tensile failure of nanotubes. Based on the parameters fitted from high-strain rate and temperature dependent molecular dynamics simulations, the model predicts that a defect free micrometer long single-wall nanotube at 300 K, stretched with a strain rate of 1%/hour, fails at about 9 plus or minus 1% tensile strain. This is in good agreement with recent experimental findings.

https://ntrs.nasa.gov/api/citations/20020052425/downloads/20020052425.pdf

Tensile strength of carbon nanotubes under realistic temperature and strain rate

A general analytic expression for the Young’s modulus of a range of carbon nanofibers (CNFs) with single or multishell nanocone or cone stacked structures has been developed from continuum elastic theory. The Young’s modulus of a single-shell nanocone is found to be cos4θ of that of an equivalent single-wall carbon nanotube (CNT). The CNFs of short lengths and small tilting angles have very large Young’s modulus comparable to that of single or multiwall CNTs, whereas the inverse is true for the CNFs with long lengths and large tilting angles. The dependence of the stiffness of CNFs on various structural parameters has been predicted by the model, validated through full-scale molecular dynamics simulations, and categorized for scanning probe tip or reinforcing fiber type applications.

Nanomechanics of carbon nanofibers: Structural and elastic properties

A theory of transport of long chain polymer molecules through carbon nanotube (CNT) channels is developed using Fokker-Planck equation and direct molecular dynamics (MD) simulations. The mean transport or translocation time tau is found to depend on the chemical potential energy, entropy and diffusion coefficient. A power law dependence tau approx. N(sup 2)is found where N is number of monomers in a molecule. For 10(exp 5)-unit long polyethylene molecules, tau is estimated to be approx. 1micro-s. The diffusion coefficient of long polymer molecules inside CNTs, like that of short ones, are found to be few orders of magnitude larger than in ordinary silicate based zeolite systems.

Chenyu Wei

Papers

Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites

Tensile strength of carbon nanotubes under realistic temperature and strain rate

Nanomechanics of carbon nanofibers: Structural and elastic properties

Theory of transport of long polymer molecules through carbon nanotube channels.

Theory of Transport of Long Polymer Molecules through Carbon Nanotube Channels