ANISOTROPIC PERCOLATION IN AN EPOXY-GRAPHITE DISC COMPOSITE

Composites comprising phi = 0.5 to 9 volume % of micron-sized graphite platelets with diameter to thickness ratios of the order of 100 have been made and deposited in the farm of partially oriented films. Room temperature electrical conductivity measurements both parallel and per pendicular to the plane of deposition reveal a low threshold of phi = 0.8 +/- 0.1 vol. %. The conductivity critical exponents are anisotrop ic with values around 7 and 10. While isotropic at the threshold, the composite system attains an anisotropy near 10(5) at the highest conce ntration limit.