Degradation of Al 2 O 3f /SiO 2 composites exposed to Na 2 SO 4 environment and MMH/N 2 O 4 bipropellants test

Al 2 O 3f /SiO 2 composites were fabricated efficiently using sol‐gel process. The degradation behavior exposed to Na 2 SO 4 environment at 1100℃ and MMH/N 2 O 4 bipropellants test were investigated and compared. The results showed that the strength of Al 2 O 3f /SiO 2 composites gradually decreased as the ratio of Na 2 SO 4 :water increased; the strength of the composites was only 23.56 MPa at 20% (Na 2 SO 4 :water), which suggested that the composites maintained lower strength. Cracks began to appear in SiO 2 matrix, and the structure of Al 2 O 3 f/SiO 2 composites could be corroded which would corrode the SiO 2 matrix, leaving naked fibers. Developing a protective layer with higher stability for Al 2 O 3f /SiO 2 composites would be considered for long time use. The composites showed higher ablation resistance to MMH/N 2 O 4 bipropellant test; the flexural strength was (77.15 ± 4.56) MPa and the retention ratio was 98.7%. The degradation of Al 2 O 3f /SiO 2 composites was promoted owing to the thermal‐mechanical and chemical factors. SiO 2 matrix became weak and fragile at elevated temperature; some SiO 2 matrix became loosened and porous after being washed away through the shearing of MMH/N 2 O 4 bipropellants, which prevented cracks from penetrating Al 2 O 3 fibers. With ongoing test, the fibers were worsened by thermal‐mechanical corrosion.