Phenomenal analysis of percolation and PTC behavior in conducting composite with short carbon fiber

In order to study the effect of the content of the short carbon fiber and the temperature on the percolation behavior of conducting composite，the equations relating the composite conductivity with the filler's volume fraction and the temperature were deduced via the Landau phase transition theory. And the percolation transition and PTC behavior in the short carbon fiber/vinyl resin composite were analyzed by these equations. The results show that the percolation threshold of composite increases with temperature as well as the PTC temperature increasing with the content of carbon fiber. The theoretical values of the percolation threshold in composite increase from 1.06% to 1.60% as the temperature from 24.6℃ to 108.4℃. And the ones of PTC temperature increase from 120℃ to 170℃ as the volume fraction of carbon fiber from 3.1% to 4.6%. The theoretical values of the percolation threshold and PTC temperature in composite fit well with the experimental data.