Ablation behavior of carbon-carbon composite nozzles produced by different carbon fibers in a small solid rocket motor

PAN-based carbon fibers produced by dry-jet wet-spun method and wet-spun method were used to produce carbon-carbon composite nozzles C-1 and C-2, the ablation properties were tested by a small solid rocket motor, then ablation morphologies were observed by scanning electron microscope (SEM), and ablation behaviors were studied. The results show that dry-jet wet-spun fibers have higher tensile strength and modulus due to the smooth surface and few defects on surface, but the interface strength with matrix is lower. The linear ablation rate of C-1 nozzle is 0.2014 mm/s under maximum pressure about 17 MPa, which is higher than that of C-2 nozzle (0.1870 mm/s). The ablation morphologies of dry-jet wet-spun fiber and wet-spun fiber are different due to the surface states, wet-spun fibers have a better resistance to mechanical erosion. The ablation testing results show that ablation of C-1 and C-2 nozzles is harsher in convergent section and throat section by the combined effect of mechanical erosion and thermochemical ablation, but slighter in divergent section by mechanical erosion. This study suggests a model to explain the ablation behavior between two kinds of fibers.