Directionality effect on mechanical properties of 3D n-directional braided (SiO2)f/SiO2 composites prepared by silica sol-infiltration-sintering method

Three-dimensional (3D) and n-directional (n = 4, 5, 6 and 7) woven (SiO₂)_f/SiO₂ composites were prepared by silica sol-infiltration-sintering (SIS) method. All the woven reinforced structures were of the same fiber content, and the prepared samples were cut in the same manner parallel to the respective braiding direction. The effect of n-direction on mechanical properties has been studied by conducting tensile, flexural and shear tests. The results showed that flexural and shear strengths of the samples increased gently with increasing n-direction from 4 to 7. However, with increasing n-direction, tensile strength initially increased steeply for 4–5 n-directions, followed by a gradual decrease for 6–7 n-directions. 3D 5-directional sample had the maximum tensile strength while 3D 7-directional sample had the maximum flexural strength and shear strength.