Mechanical analysis of a stitched sandwich structure and its SiO_2f/SiO₂ panels: Experimental and numerical investigation on compression and shear performances

The compression and shear performances of the stitched sandwich thermal protection structure (SSTPS) was systematically investigated through experimental and simulation methods in this study. Compression and shear testing methods were designed, and macroscopic performance data for SiO_2f/SiO₂ thin panels and SSTPS were successfully obtained, thereby validating the rationality of the experimental approach. By establishing mechanical experimental methods, the correlation between microscopic structural features and macroscopic mechanical performance was revealed, and mechanical modeling and analysis work was conducted. The experimental and numerical results indicate that compression and shear failure of thin panels mainly occur at the intersections of fiber bundles, exhibiting non-brittle failure. The delamination of sandwich materials or the buckling deformation of panels is identified as the primary cause of the nonlinear response in SSTPS. Elevated temperatures induce an increase in the modulus and strength of SSTPS and a decrease in toughness, correlated with the high-temperature densification of the matrix structure. Finite element simulations reveal the critical role of component and interface damage in macroscopic nonlinear mechanical responses. The research demonstrates that, the compressive and shear failure mechanisms of SiO_2f/SiO₂ thin panels and SSTPS were successfully elucidated through the implementation of an innovative experimental methodology.