Thermo-Structural Analysis And Failure Behavior Of C/C Composite Throat

As one of the key components of solid rocket motor, it is not only to withstand high temperature and pressure, but also to withstand the erosion of the solid particles and thermal chemical erosion of hot gas. Poor working environment brings seriously impact to the safety of throat of solid rocket motor which is essential to safe working of solid rocket motor. In this paper, C/C composite nozzle throat of solid rocket motor was used as the research object, using of ABAQUS finite element software, established a calculation method of thermal structure of the throat which considered the contact resistance, ablation moving boundary and interface debonding and other factors. What's more, this paper revealed the key failure factors of the throat and studied the failure behavior of the throat.First, this paper analyzed the temperature field of the throat. The contact resistance and ablation moving border were taken into account in the calculations and analyzed their impact on the temperature field. The results showed that when contact resistance was greater than 1×10^-4m²·℃/W, it had great impact on the temperature field and must be considered when the temperature field was calculated. When the contact resistance was less than 1×10^-4m²·℃/W, its effect is not very clear and can be ignored in the calculation of the temperature field. Ablation moving boundary had small impact on the temperature field of inner wall of the throat, but had great impact on the temperature field of outer wall and with the working time increasing, the influence was more and more evident obvious. Then the temperature field was calculated with synthesized of the two factors.Secondly, on the basis of temperature field, using of sequential coupling method, calculated the stress field of the throat. The contact resistance, ablation moving border and interface debonding were taken into account in the calculations and analyzed their impact on the stress field. This paper also analyzed the extreme value characteristics of radial and axial stress which appeared before and after debonding. The results showed that the contact resistance's impact on the stress field was same as the impact on the temperature field; ablation moving boundary had great impact on the stress field of outer wall of throat, and its impact on radial stress was greater than axial stress. Then the stress field was calculated with synthesized of all factors. The results showed that when the working time was 43s, radial tensile stress was 88MPa, compressive stress was 189MPa; axial tensile stress was 71MPa, compressive stress was 144MPa.Finally, based on the analysis of the temperature field and stress field, the failure behavior of the throat was studied with the extended finite element method. The results showed that under the action of thermal stress, the throat would appear rupture destruction; extrusion action which the throat acted on exit cone could lead to integral fracture of exit cone; interface debonding phenomenon will lead to appearing narrow gap between the throat and the back wall and staggering between the throat and exit cone. The research of failure mode had certain practical value to structure design and material selection of the solid rocket motor throat.