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Viscous flow behavior of silica melts on an uncooled carbon/silicon carbide composite nozzle was investigated in the combustion environment of a liquid-fueled rocket engine simulated by an ethanol/oxygen combustion gas generator. The results showed that severe ablation of the nozzle throat were attributed to flow downstream and blow-off of the silica scales derived from vigorous oxidation of the silicon carbide matrix. The viscous flow behavior of the silica was determined by both the intrinsic viscosity of silica melts and the external aerodynamic forces of the combustion gas. [ABSTRACT FROM AUTHOR]

Abstract: The erosion resistance of the needled carbon/carbon composite leading edge was investigated by exposure to the solid rocket motor (SRM) plume. The erosion morphology and microstructure were examined and associated erosion mechanisms discussed. The composite leading edge was severely damaged with large recession and erosion rate after exposure. The results suggest that the erosion behavior was determined by the weak needling structure of the leading edge windward with small thickness in the severe environment of the plume impingement. Erosion mechanisms were combined effects of thermochemical ablation by oxidizing species and thermomechanical erosion by both aerodynamic force and alumina particles. The former weakens the strength of the composite while the latter contributes primarily to high erosion rate in the oxy-lean SRM plume environments. [Copyright &y& Elsevier]

Abstract: The ablation of pierced C/C composite nozzles was investigated via hot-fire testing by an oxygen/ethanol combustion gas generator simulating combustion environments of the liquid rocket engine. Ablation microstructures and mechanisms of the composite nozzle were discussed. The results showed that both linear ablation rate and mass ablation rate increased with increasing mass ratio of oxygen/ethanol. The ablation of the pierced C/C composite was attributed to the heterogeneous reactions between carbon and oxidizing species and could be interpreted by the thermochemical ablation model. The ablation rate of the composite was determined by both chemical kinetics and diffusion. The ablation of the composite resulted in cone-shape carbon fibers and shell-shape matrix with pits and grooves left on the surfaces. [Copyright &y& Elsevier]