Carbon nanotube-reinforced composites mechanical properties

Carbon nanotubes are long cylinders of covalently bonded carbon atoms and have a diameter from a few angstroms to several tens of nanometers. Carbon nanotubes have exceptional mechanical properties [47-50], and extensive research work has been carried out on carbon nanotube-reinforced polymer composites [46-52]. However, weak interfacial bonding between carbon nanotubes and polymers leads to poor stress transfer, and this has limited the full realization of carbon nanotubes as reinforcements for polymers. Therefore, chemical functionalization of carbon nanotubes has been conducted. 

For CNTs not well bonded to polymers, Jiang et al. [137] established a cohesive law for carbon nanotube/polymer interfaces. The cohesive law and its properties (e.g., cohesive strength, cohesive energy) are obtained directly from the Lennard-Jones potential from the van der Waals interactions. Such a cohesive law is incorporated in the micromechanics model to study the mechanical behavior of carbon nanotube-reinforced composite materials. CNTs indeed improve the mechanical behavior of composite at the small strain. However, such improvement disappears at relatively large strain beeause the eompletely debonded nanotubes behave like voids in the matrix and may even weaken the composite. The increase of interface adhesion between CNTs and polymer matrix may significantly improve the composite behavior at the large strain [138]. 

Another method to improve the mechanical properties such as interfacial strength is to add nanosized carbon fiber-reinforced particles into the composite [18-20]. A strong influence of a uniform dispersion of the small-sized fibers or partides on the composite properties of advanced nanocomposites, such as carbon nanotube-reinforced composites was also reported [21-24]. However, few papers mention the enhancing method for improving the interfacial adhesion between fiber and matrix in a natural BF composite. 

Seidel, G. D., Lagoudas, D. C. Micromechanical analysis of the effective elastic properties of carbon nanotube reinforced composites, Mech of Mater, 2006, 38,884-907. Z. Hashin and, B. Rosen. The elastic moduli of fiber-reinforced materials. 1964, Journal of Applied Mechanics 31,223-232. 

Biercuk MJ, Llaguno MC, Radosavljevic M, Hyun JK, Johnson AT (2002). Morphological and mechanical properties of carbon-nanotube-reinforced semicrystalline and amorphous polymer composites. Appl. Phys. Lett. 80 2767-2769. 

Concerning carbon nanotube-reinforced silicon nitride matrices, only a few reports have so far been published [19]. In this case, hot isostatic pressing has been used for composite processing. The carbon nanotubes remained in the microstructure only under low pressures (2 MPa) they connect the silicon nitride grains and produce a 15-37% improvement of the mechanical properties as compared with other carbon-filled samples (Fig. 19.11). Increase of pressure... 

Poly(vinyl) alcohol (PVA) is a semi-crystalline polymer, which is already widely used for various applications, either under the form of films or fibers. Compared to other polymers, as it is water-soluble at high temperature, it is easy to process from aqueous solutions. Carbon nanotubes can also be dispersed or solubilized in water via different functionalization approaches. It was quite natural for researchers to try to mix carbon nanotubes and PVA to improve the properties of the neat polymer. In this chapter, we will first examine the different methods that have been used to process CNT/PVA composites. The structures and the particular interaction between the polymer and the nanotube surface have been characterized in several works. Then we will consider the composite mechanical properties, which have been extensively investigated in the literature. Despite the number of publications in the field, we will see that a lot of work is still to be done for achieving the most of the exceptional reinforcement potential of carbon nanotubes. 

F. Ye, L. Liu, Y. Wang, Y. Zhou, B. Peng, and Q. Meng, Preparation and mechanical properties of carbon nanotube reinforced barium aluminosilicate glass-ceramic composites. Script. Mater., 55, 91 M (2006). 

Tai, N.-H., Yeh, M.-K., and J.-H. Liu. 2004. Enhancement of the mechanical properties of carbon nanotube/ phenolic composites using a carbon nanotube network as the reinforcement. Carbon 42 2774-2777. 

AyatoUahi, M. R., Shadlou, S., and Shokrieh, M. M., Multiscale modeling for mechanical properties of carbon nanotube reinforced nanocomposites subjected to different types of loading. Composite Structures, 93, 2250-2259 (2011). 

Mathur, R. B. Pande, S. Singh, B. P. Dhami, T. L. Electrical and mechanical properties of multi-walled carbon nanotubes reinforced pmma and ps composites. Polym. Comps. 2008, 29, 717-727. 

Xiao, K. Q. Zhang, L. C. Zarudi, I. Mechanical and rheological properties of carbon nanotube reinforced polyethylene composites. Comp. Sci. Technol. 2007, 67, 177-182. 

To summarize, the mechanical properties of carbon nanotube reinforced polymer composites mainly depend on the following factors ... 

Liu T X, Phang I Y, Shen L, Chow S Y and Zhang W D (2004) Morphology and mechanical properties of multiwalled carbon nanotubes reinforced nylon-6 composites, Macromolecules 37 7214-7222. 

Zeng, H.L. Gao, C. Wang, Y.P. Watts, P.C.P. Kong, H. Cui, X.W. Yan, D.Y. (2006a). In situ polymerization approach to multiwalled carbon nanotubes-reinforced nylon 1010 composites Mechanical properties and aystaUization behavior. Polymer, 47, 113-122. 

The importance of promoting better knowledge in the field of polymer composites is demonstrated by the contents of this volume, which contains 18 Independent chapters. The first part of this volume deals with the topic of structure and properties of polymer nanocomposites. In Chapter 1, Schulte et al. review the state of the art of carbon nanotube-reinforced polymers. The opportunity to apply carbon nanotubes as a filler for polymers and the improvement of the mechanical and functional properties are discussed. The application of non-layered nanoparticles in polymer modification is described by M. Q. Zhang et al. in Chapter 2. A grafting polymerization technique is applied to inorganic nanoparticles, which helps to provide the composites with balanced performance. Chapter 3, authored... 

Koratkar, N., Wei, B., Ajayan, P. - Multifunctional structural reinforcement featuring carbon nanotube film . Composites Sci. Technol. 63 (2003) 1525-1531 Binnott, S., Shenderova, O., White, C., Brenner, D. - Mechanical properties of nanotubule fibres and composites determined from theoretical calculations and simulations , PH 80008-6223(97)00144-9... 

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