C/C复合材料微观尺度烧蚀过程质量损失速率模拟

Simulation on mass loss of C/C composites ablation with fiber scale

基于水平集算法,耦合扩散方程建立了C/C复合材料在微观尺度下的2D轴对称烧蚀模型,计算了C/C复合材料的微观形貌演变过程,并将形貌演变至稳态的计算结果与C/C复合材料实际烧蚀后的微观形貌进行了对比,二者吻合较好,验证了该模型的可靠性。进而分析了气体扩散和非均匀氧化反应对纤维和基体的相对质量损失速率的影响规律。研究表明,随着Sherwood数Sh的降低纤维的质量损失速率会迅速增大,基体的相对质量损失速率会迅速降低,二者均在烧蚀形貌达到稳态前稳定;纤维和基体的相对质量损失速率达到稳态所需时间随反应速率比A的增大而增大。

In the present study,a 2D axisymmetric ablation model for C/C composites at microscale was built based on the coupling of level set method and diffusion equation,and then the evolution of ablation morphologies of C/C composites were calculated.The calculated results of morphology evolution to steady state were proved to be in good agreement with the surface morphologies of C/C composites after ablation,illustrating the reliability of the model.Relative mass loss rates between fiber and matrix during ablation process under gas diffusion and heterogeneous oxidation mechanism were analyzed. With the decrease of Sh,mass loss rate of fiber was increased quickly,whereas the mass loss rate of matrix was decreased.Mass loss rates of fiber and matrix were increased with the increase of A during ablation process.