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One-Dimensional Modeling of the Carbon-Phenolic Composite Process Under Thermal Heating

Ahsanzadeh, Hamid Reza | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58435 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hosseini Kordkheili, Ali
  7. Abstract:
  8. This research focuses on the development of an advanced numerical model for analyzing the behavior of ablative composites used as sacrificial materials in high-temperature environments. Ablative composites protect underlying materials from extreme heat through unique protective mechanisms, including endothermic reactions, char layer formation, and the production of cooling gases. The model presented in this study comprehensively simulates the following complex multiphysics phenomena: multi-mechanism heat transfer (conduction, radiation, and convection), chemical reactions (pyrolysis, char formation, and surface oxidation), the dynamics of volatile gases, and structural changes (density variation, porosity, and surface recession), along with changes in thermophysical properties (thermal conductivity and specific heat capacity).This study implements an integrated multi-coupling between the temperature field, the kinetics of chemical decomposition, and the dynamics of the produced gas flow. In this strong interaction, the temperature field directly influences the rate of pyrolysis and gas production chemical reactions. The produced gases, in turn, modulate heat transfer through forced convection within the pores, forming a complete feedback loop. This advanced coupling enables a more realistic simulation of the formation and evolution of the protective char layer and its role in thermal insulation.An efficient combined numerical method is employed in this research, where the heat transfer equations are solved implicitly using MATLAB's nonlinear fsolve solver. This approach ensures high accuracy in calculating steep temperature gradients while maintaining the stability of the method. The material kinetics and gas production equations are computed using an explicit method. The MATLAB environment was chosen as the primary platform for model development, providing high modularity and flexibility for defining temperature-dependent properties and implementing numerical solution algorithms. Simplifying assumptions were also made for the solution, such as no surface recession and constant porosity.The results obtained from the model were validated against experimental data and Henderson's numerical data. Graphs of temperature versus time at different depths and temperature versus location at different times show very good agreement with experimental data. The model's calculated temperature error was found to be around 4%, indicating the high accuracy and reliability of the developed model
  9. Keywords:
  10. Pyrolysis ; Heat Flux ; One-Dimentional Modeling ; Carbon/Phenolic ; Mechanical Properties ; High-Tempreture Mechanical Property ; Thermal Protection System (TPS) ; Heat Resistance

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