Ablation and thermal degradation behaviour of a composite based on resol type phenolic resin: Process modeling and experimental

During atmospheric re-entry, ballistic or space vehicle is subjected to severe aerodynamic heating and its successful return through the Earth's atmosphere depends largely on the provision that is made for reducing aerodynamic heat transfer to its structure. For this purpose ablative heat shield is normally used which undergoes physical, chemical, and mostly endothermal transformations. These transformations produce new liquid or gas phases which are subsequently injected into the environment. Mass and energy balance equations have been solved in order to model the ablation and thermal degradation behaviour of an ablative composite. A method to determine and calculate some of the parameters in the ablative equation is proposed from the simultaneous thermal gravity and differential scanning calorimetry analysis techniques. The objective of this work is to model ablating, charring and thermal degradation behaviour of a heat shield resol-type phenolic resin/asbestos cloth composite in oxyacetylene flame test. This requires solving serious heat transfer equations with moving boundaries. Explicit forward finite difference method (FDM) is used for heat transfer calculation. Moving boundaries are fixed by the Landau transformation. The ablation equation has been solved numerically. Temperature distribution through the composite thickness, temperature of moving surface, and the rate of moving boundary changes are evaluated. The results are in a good agreement with the experimental data obtained from oxyacetylene flame tests. The model can successfully be used for both material selection and thickness calculation in the design of thermal protection shields. (c) 2006 Elsevier Ltd. All fights reserved.