Ablation behavior of Al20Si/graphite composite nozzle-throats in a solid rocket motor environment

Small solid rocket motors (SRM) require low density, low ablation nozzle-throat materials. In the present study, Al20Si alloy was infiltrated into the porous graphite matrix to develop Al20Si/graphite composites by pressure infiltration method. The ablation behavior of the as-prepared composite was investigated in a small SRM testing system with an average pressure of 13.3 MPa and 5 wt% Al for 1.4 s. The results show that the linear ablation rate of the Al20Si/graphite throat decreased by 92% compared to that of the C/C composite throat. The increased anti-ablative properties are provided by Al20Si alloy fillers, which reduce the degree of thermochemical ablation of the graphite matrix through heat dissipation, oxygen dissipation, and thermal blockage. Furthermore, the Al₄SiC₄ generated from Al20Si alloy and graphite fills graphite pores, which contributes to the oxidation resistance of the composite.