Abstract
A procedure was developed to predict burn-off of a carbon-fibre reinforced composite material based on observation of weight change during isothermal oxidation at various temperatures in air and in oxygen/nitrogen gas mixtures of various partial pressures of oxygen. The oxidation process was composed of four stages, of which the second and the third were significant in practice. The rates of oxidation (Vr) at every oxidation temperature were approximated in terms of the extent of burn-off (x) by log Vr=loga+b·x for both the second and the third stages of the oxidation in air, while they were by log Vr=logV0 for the second and by log Vr=logα+β·logx for the third stages of oxidation in the gas mixture at every partial pressure of oxygen. Here a, b, α, β and V0 are constants and vary with the oxidation temperature and the partial pressure of oxygen. The variation of the values of the constants with the oxidation temperature etc. were established based on the experimental data. Burn-offs in certain oxidation conditions were calculated by numerical integration of the obtained equations. The calculated burn-offs agreed well with the observed ones.
