Effect of Different Sewing Density On Mechanical Properties of 2D SiC/SiC Composites

with the advantages of low textile processing cost, short period and excellent in-plane mechanical properties, the 2D SiC/SiC composites has become one of the most potential structure in engineering application. In this article, base on automatic CNC sewing system and lock stitch method, the SiC fiber preform is sewed by SiC fibers with different sewing density. The sewing 2D SiC fiber preform with PyC interface is densified by polymer infiltration and pyrolysis (PIP) method. The microstructure of 2D SiC/SiC composites is characterized by micro-CT and scanning electron microscope (SEM). Specifically, for the sewing densities of 5mm, 7.5mm, 10mm, 12.5mm, and 15mm, the average flexural strength at room temperature was 378.8 MPa, 447.1 MPa, 485.6 MPa, 504.0 MPa, and 521.5 MPa, and the average tensile strength at room temperature was 261.6 MPa, 286.4 MPa, 293.8 MPa, 300.5 MPa, and 306.5 MPa, respectively. The average interlayer shear strength at room temperature was 84.7 MPa, 76 MPa, 70.2 MPa, 63 MPa and 54.4 MPa, respectively. The results show that with the increase of sewing density, the densification process is affected by the bending of the preform, which leads to the decrease of the in-plane tensile and flexural strength of the composites at room temperature, but the increase of interlaminar shear bearing fibers increases the interlaminar shear strength of the composites at room temperature.