Modelling carbon fibers oxidation in air at constant heating rates

Abstract

Modelling of carbon fiber (CF) oxidation in air, at 25°–1000°C and heating rates ( HR) of 1°, 2°, 5°, 10°, and 20°C/min, has been performed. A simple thermogravimetric analysis technique has been used to examine the oxidation kinetics of three carbon fibers: a carbonized polyacrylonitrile fiber, a graphitized pitch fiber, and a graphitized rayon fabric. The modelling involved development of four main empirical eqns correlating HR to T 0.5, BO to T/ T 0.5, HR to R max , and R/ R max to BO. T 0.5 is the temperature attained when 50% of the CF gasifies, BO is the fractional burn-off at a given temperature, T, and R max is the maximum rate ( R) of oxidation mg/g starting CF.min. These eqns can predict the recession of a carbon fiber component without the need to include a surface area term in the analysis. The technique and proposed analysis, which can be used to screen a vast number of CF in a relatively short time, yield information on oxidation kinetics, activation energy, and the rate-determining step.