Percolation behavior of conductor-insulator composites with varying aspect ratio of conductive fiber

The electrical properties of composite electroceramics are determined by the concentration, shape and distribution of filler phase in matrix. The carbon fiber-filled polymer was chosen as a model system and the electrical conductivity was measured as a function of carbon fiber content and the aspect ratio (AR) of the fibers to understand the percolation behavior of the composites. The composites of carbon fiber (1 similar to 9 vol.%) and thermoplastic polymer were fabricated in a mold press with the aspect ratio of carbon fiber varying between 4 and 10. The percolation threshold volume concentrations (V-c) of transition from the insulator to the conductor decreased as the fiber aspect ratio increased. With the fibers segregated at the polymer-polymer interfaces in the present study, V-c values were much smaller than those with the fibers randomly distributed in the matrix shown in other studies. The inverse relation between V-c and AR was found as expected. From the comparison with other experimental and simulated data, we concluded that the slope in 1/V-c versus AR plot is a strong function of fiber segregation.