Why Use Nanotubes in Nanocomposites

Mechanical properties - Numerous theoretical works have been done to predict the mechanical properties of reinforced composites. Some of these models are more sophisticated, but in order to understand why nanotubes are ideal reinforcement particles, the rule of 

In this expression, Ef and Em are the Young modulus of respectively the fiber and the matrix, and t f is the fiber volume fraction. //0 is the fiber orientation factor this factor is equal to 1 for perfectly oriented fibers and 1/6 for a random orientation, tj, is the so-called effective length coefficient (10), which mainly depends on the aspect ratio of the fiber. Indeed  

This factor approaches 1 for aspect ratios above 10, pointing out the importance of using high aspect ratio fillers. 

A very similar expression can be derived to calculate the composite strength  

This model shows that the requirements for a good reinforcement are a high volume fraction of very well oriented fibers and with high aspect ratios. Nanotube aspect ratios are varying, but are very large, from at least 50 for the shorter and thicker nanotubes to sometimes more than 1000 for the longer and thinner ones. 

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