Stability behavior of a novel 3DC C/Y2Si2O7 composites in vacuum at high temperature

This study presents a novel laminated stitched three-dimensional carbon cloth preform-reinforced Y 2 Si 2 O 7 composite (3DC C/Y 2 Si 2 O 7 ), fabricated via sol infiltration heating (SIH) using a high stability and yields Y 2 O 3 -SiO 2 sol precursor, designed for high-speed aircraft operating in both atmospheric and low-pressure vacuum near-space conditions. The composite demonstrates superior mechanical properties, with flexural strength, fracture energy, and fracture toughness values of 334 ± 18.1 MPa, 15.3 ± 1.3 kJ/m 2 , and 17.4 ± 0.7 MPa m 1/2 , respectively—marking improvements of 258.1 %, 3686.7 %, and 861.4 % over monolithic Y 2 Si 2 O 7 . It exhibits excellent thermal stability under vacuum environment (pressure ≤10 Pa), retaining over 95 % of its mechanical properties after 10 h at 1300 °C without microstructural or phase changes. Even after 5 h at 1400 °C, it maintains more than 75 % of its performance, despite minor SiO 2 evaporation and fiber deterioration. The β- to γ-Y 2 Si 2 O 7 phase transformation induces no detrimental stresses due to matched thermal expansion between monoclinic phases. These results affirm the composite's suitability for high-temperature applications under vacuum, indicating strong potential for advanced aerospace thermal components.