Mechanical properties and microstructure of 3D orthogonal quartz fiber reinforced silica composites fabricated by silicasol-infiltration-sintering

Highlights: ► QFSCs have become a promising candidate material in aerospace vehicles. ► Fabrication temperature of the composites was relatively low. ► SIS process could be a promising method to fabricate CFCCs. ► 3D orthogonal QFSCs display good mechanical properties and ideal microstructure. -- Abstract: 3D orthogonal quartz fiber reinforced silica composites were fabricated by silicasol-infiltration-sintering method at a low temperature of 450 °C, and the mechanical properties and microstructure of the composites were investigated. The density of the composites was 1.71 g/cm3, the average values of flexure strength and shear strength of the composites were 29.4 MPa and 14.8 MPa at room temperature, respectively. Both of the failures under flexural loading and shear loading were not catastrophic. Compared with α-quartz and α-cristobalite, the fracture toughness of 3D orthogonal quartz fiber reinforced silica composites has been enhanced by a wide margin. The damage features of the composites are identified, using digital camera and scanning electron microscopy. There was a good state without serious degradation of quartz fibers during the preparation. The bonding between the matrix and the incorporated fibers is weak, and the matrix cracks propagate along the weak interface. Apart from this, the composite is found to exhibit an extensive and long fiber pull-out in the fracture surface. Crack deflection and fiber pull-out contributed to the good toughness of the composite under the loading.