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To develop and carry out calculations of heat transfer in heat-shielding materials, it is necessary to study the mechanisms of material destruction. For a composite material, it is important to study the behavior of both the material as a whole and each of its components. The work is devoted to the study of thermal oxidative degradation of highly porous material based on chopped carbon fibers, which is the preform for making advanced carbon-ceramic composite materials. The study was conducted in an oxidizing air environment using simultaneous thermal analysis with varying the initial mass of the samples and at different heating rates (5, 10, 20 K/min). The dependences of thermal effects in the material and mass loss during destruction for each sample were obtained. The influence of variable parameters on the temperature of the beginning of material destruction and the steady removal speed was established. It is shown that the destruction of the material occurs in the surface layer of a certain thickness. According to the results of thermogravimetric studies with different heating rates, a generalized kinetic model of destruction was developed and the kinetic characteristics of destruction were determined.

The simulation results of the thermal stabilization of polyacrylonitrile pressed organomorphic frame samples are presented. The local temperature maximum in the sample depth due to an exothermic oxidation reaction was confirmed. The possibility of the avalanche exothermic effect, which can lead to a sample burnout, is demonstrated theoretically. The analysis of the influence of the initial fiber oxidation degree on the sample temperature state have been carried out.

Simulation and analysis of thermophysical processes in PAN-fiber-based pressed samples that occurs during thermal stabilization were carried out. It is significant fact from the heat transfer point of view that the heat stabilization process proceeds with a definite exothermic effect. Herewith a strongly pronounced coupling between both the intensity of heat generation and the temperature level and heating rate at each point of the sample was observed. The influence of the main factors that effects on the sample temperature state, such as the density and thermal conductivity of the preform material, also the rate constants of the thermal stabilization process, was studied. The experimental data of the sample temperature state in the thermal stabilization process is presented and was compared with the analysis results.