Effect of stress on the steady state ablation morphology of C/C composites

During the ablation process in the thermal protection system, carbon/carbon (C/C) composites exhibit a characteristic steady state ablation morphology that includes needle-like fibers and sheath-like matrix, with deep depressions between the fibers and matrix. A theoretical explanation describing the formation of inherent steady state ablation morphology of C/C composites is proposed and we suggest that the radial thermal stress at the interface between the fibers and matrix affects the ablation thermochemical reaction of the interphase. Then, a quantitative relationship between stress and the ablation velocity of the interphase is proposed based on the mechanical coupling theory and a mesoscopic theoretical analysis model including mechanochemical coupling relationship of the steady state ablation morphology of C/C composites is established. In the mesoscopic model of steady state ablation morphology, the effect of stress on the steady state ablation morphology of C/C composites is analyzed. The results reveal that stress plays a significant role in determining the steady state ablation morphology of C/C composites, with its influence being comparable to that of material properties. Moreover, this work can be extended to further explore the ablation behavior of other ablation thermal protection composites. These findings provide valuable insights into understanding the interactions between different phenomena occurring during the ablation process of C/C composites.