The effect of Z-yarn density on the in-plane shear property of three-dimensional stitched carbon fiber reinforced silicon carbide composites

Three types of three-dimensional stitched carbon fiber reinforced silicon carbide composites (3DS C/SiCs) were fabricated by chemical vapor infiltration with the Z-yarn density of 4, 9, and 16 stitching/cm2 (S4, S9 and S16). The results showed: 3DS C/SiCs with different Z-yarn densities had identical damage mechanism which was referred to as rigid body sliding. The fracture surfaces of both S4 and S9 lied in the stitched line plane. However, S16 exhibited the fracture morphologies of plane rise. Compared with that of S4, the in-plane shear strengths of S9 and S16 increased by 13.1% and 37.5%, respectively. However, the shear moduli of them decreased by 22.2% and 36.4%. Benefitted from the studies of Turner, a formula was proposed to well predict the in-plane shear strength of 3DS C/SiCs with different Z-yarn density. Although they exhibited low in-plane shear strength, 3K 3DS C/SiCs would not alleviate the notch sensitivity through shear stress redistribution. However, the application of them with lower Z-yarn density should be avoided. The similar conclusions as listed above may be also attained for other Z-reinforced ceramic-matrix composites because 3DS C/SiC is a representative of them.