Percolation in short-fiber composites: Cluster statistics and critical exponents

The influence of microstructure on the percolation process in short-fiber composites has been examined in terms of the cluster statistics measured in a 3D continuum system. Simulation results are presented for a distributed fiber length system, in contrast to the results reported in the literature for uniform fiber lengths. The critical percolation exponents for the 3D continuum short-fiber composite system were found to compare well with those of 2D and 3D lattice systems reported in the literature. A fractal dimension of 2.3 was calculated from the above critical exponents as well as from the growth of the radius of gyration of the fibrous clusters. As expected the fractal dimension increased as the fiber orientation in the clusters changed from a preferentially aligned one (as observed in injection-molded composites) to a more random microstructure (as observed in compression-molded composites). (C) 1997 Elsevier Science Limited.