Mechanical properties of random arrays of short carbon fibers

Abstract
The mechanical properties of random short carbon fiber composites have been studied experimentally in relation with the electrical properties (continuity) in three different states : 1) fibers in a hard expoxyde matrix, 2) fibers in a well formed gel, 3) fibers sediment in a viscous liquid. Although there is no precise correlation between the electrical percolation threshold and the continuous increase of elastic modulus with fiber concentration, the variation of linear elastic properties can be seen to be more and more related to the connectivity (and possibly entanglement) transition when going from state 1 to 3, i.e. as the influence of the matrix decreases. A related discussion dealing with entanglement properties and mechanical percolation is presented