We show that a generalized connectedness percolation theory can be made tractable for a large class of anisotropic particle mixtures that potentially contain an infinite number of components. By applying our methodology to carbon-nanotube composites, we explain the huge variations found in the onset of electrical conduction in terms of a percolation threshold that turns out to be sensitive to polydispersity in particle length and diameter. The theory also allows us to model the influence of the presence of nonconductive species in the mixture, such as is the case for single-walled nanotubes, showing that these raise the percolation threshold proportionally to their abundance.

• Received 25 August 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.225704