Effect of Densification on the Impact Behavior of SiO2f/SiO2 Woven Ceramic Matrix Composites Filled with Silica Aerogel

Woven silica fiber-reinforced ceramic silica matrix composites with 2.5 dimensionality (2.5D woven SiO2f/SiO2 CMCs) offer various advantages and are commonly utilized in the aerospace industry. The CMCs are primarily prepared using the sol-gel process including infiltration, drying, and sintering under a certain temperature for several cycles. The infiltration effect is influenced by the pore diameter distribution inside the silica matrix, the silica matrix geometry, porosity inside silica matrix, and the silica sol viscosity according to Washburn equation for capillary rise. The physical properties of fiber, matrix, and the interfacial properties are important factors for the mechanical performance of CMCs. The mechanical strength of the CMCs matrix can be enhanced by densification to increase the contact area between the silica fiber tows and silica matrix. Silica aerogels are prepared by proportioning different molar ratios of ethyl-cool orthosilicate, anhydrous ethanol, and deionized water. The porosity of CMCs specimens filled with silica aerogel is around 0.88-9.02%, which is lower than that of specimens without silica aerogel (20-25%). Therefore, woven SiO2f/SiO2 CMCs have a fill ratio of 90.98-99.12%. The compressive impact process was simulated with finite element analysis (FEA), and the split Hopkinson pressure bar (SHPB) compressive impact test for the CMCs specimens showed improvement in the anti-impact mechanical properties of CMCs. The densification effect on CMCs specimens filled with silica aerogel was examined and analyzed via SEM imaging. Upon comparison, the simulation results show good consistency with the experimental stress-strain curves and failure modes results, indicating that the compressive impact behaviors can be efficiently predicted with FEA.