Research on performance of thermal protection systems is significant for the development of products for aerospace applications, such as internal insulation for solid rocket motors, nozzles, and external thermal protection insulation. Ablative materials are used as sacrificial material against the combination of high temperatures and high heat flux to the protected vessel. The unique chemical and physical characteristics of these materials face successfully the thermo-chemical ablation and mechanical erosion of the surface. Variation of thermal conductivity with temperature cannot be predicted, and there is a need to determine it experimentally. Since most reactions which influence the thermal conductivity of the ablative material occur up to a temperature of 1200K, it was decided to develop such an apparatus.
In the present work, the development of a thermal conductivity apparatus for research of ablative materials is presented. Derivation of a semi-empirical model for determining the instantaneous thermal conductivity of the ablative material has been implemented successfully. Verification testing of the apparatus was carried out in order to determine the accuracy and sensitivity of results. Four compositions of EPDM-based insulation in addition to PTFE as a reference material were tested. Results were compared to relevant results from the literature and to a well-established apparatus, revealing good agreement. It was found that it is possible to determining the specific heat as well as the thermal diffusivity of the ablative material, once the temperature dependent density is experimentally determined. The conducted experiments revealed the influence of the following parameters on the temperature dependent thermal conductivity: Curing agent of the ablative material, reinforcing fibers and fire retardant agents.
