Numerical Simulation Of Ablation Behavior Of Thermal Protective Composites

Thermal protective composites have excellent high temperature performance. The material takes away a lot of heat and reduce the heat transfer to the inside structure through ablation, which effectively protect the internal structure and have the effect of the thermal protection. So the research of thermal ablation behavior of composite materials has important application value in the field of engineering.Thermal protective composites will occur a series of physical and chemical reaction in high temperature, high enthalpy and high pressure environment, which produce quality loss due to material ablation. The composites were analyzed by thermal chemical ablation mechanism. The principles of conservation of energy, mass conservation principle, the principle of thermal chemical reaction equilibrium are coupled to thermal chemical ablation model. A moving boundary exists in the process of materials ablation time, so, we need to solve the temperature field of composite materials under ablation moving boundary conditions.Finite element numerical simulation method is the most commonly used method to solve complex engineering problems. All kinds of finite element calculation software have been developed according to different engineering applications. In addition, the finite element numerical analysis software also provide powerful post-processing function in the numerical analysis of the research question, which can be convenient for analyzing and discussing the calculation model. In research work of this paper, different thermal protective composites ablation model is established through the finite element numerical calculation software, and the finite element grid was divided to the structure, and finally the finite element numerical calculation results are studied and analyzed.Thermal protective composites will occur thermo chemical ablation and a series of physical and chemical changes. The thermal chemical reaction of carbon composite material is numerically calculated using the principle of chemical equilibrium under the condition of high temperature, also, the ablation products distribution under different surface temperature was analyzed. Temperature field of carbon/carbon composites under the action of thermal chemical ablation was calculated and analyzed by finite element numerical simulation methods. Carbon composite material will react with air components under high temperature environment, mainly including carbon oxidation reaction, the sublimation of carbon and carbon and nitrogen. Temperature field of carbon/carbon composites was numerically analyzed under the action of the ablation. The ablation surface heat flow was calculated through the principle of thermal chemical ablation and the surface energy balance, and its temperature field is calculated and analyzed coupling the internal heat conduction equations. The receding ablation surface under the environment of high temperature was numerically simulated. Temperature field distribution of carbon/carbon composites was calculated under moving ablation boundary conditions.In this paper, according to the analysis of the thermo-chemical mechanism, the change rules of ablation properties of C/C composites in thermo-chemical ablation, ablation surface receding and temperature field coupling was investigated by finite element method. Achieved the receding of the ablation boundary by virtual failure and rebuilding orphan mesh part, and established finite element model of ablation temperature field at receding boundary conditions. The net heat flux flowed into the material and ablation rate was calculated by thermo-chemical ablation theory. The phenomenon of large local heat flux on the irregular surface was corrected by programming after ablation surface receding when the heat flux was reloaded. Research shows that as the ablation time increases, the heat flux flows into composite materials will reach a dynamic balance. The ablation of the material is the results of a variety of factors and coupled calculation can truly reflect the characteristics of the ablation of the material.For revealing the detailed response of thermal protective composites in the process of internal carbonization, the carbonized ablation process of carbon/phenolic composite materials is analyzed by the method of finite element numerical simulation. The ablation surface receding is achieved by ALE moving mesh methods. The internal material pyrolysis in process of ablation is established by Arrhenius laws. The internal pyrolytic reactions, temperature distribution, the changes of carburization zone and material properties are coupling calculated when the ablation occurs. Research results show that the pyrolysis of the material is penetrated from ahlation surface to inner materials. The degree of pyrolysis reaction decreased with time. Internal quality loss happens through incessancy penetrating of the internal material pyrolysis, which cause the material been divided into carburization zone, pyrolytic zone and original material zone. Charring ablative material played an effective thermal protection function under coupling of a variety of factors.