Mechanical response and damage mechanism of 2D woven SiCf/SiC ceramic matrix composites under tension-shear coupling load

The macroscopic mechanical behavior and coupling damage mechanism of 2D woven SiCf/SiC ceramic matrix composites (CMC) prepared by chemical vapor infiltration (CVI) process under tension-shear coupling load were experimentally analyzed. At macroscale, the uniaxial tension, uniaxial shear and off-axis tension tests were completed and the results were compared. The tensile modulus and proportional limit have no significant dif-ference with the increase of off-axis angle, while failure strength decreases by 22.3% compared the 45 degrees tensile (165.4 MPa) with the 0 degrees tensile (212.8 MPa). Based on the strain-difference analysis, the coupling damage effect of SiCf/SiC-CMC was characterized. At microscale, the main damage types of SiCf/SiC-CMC during loading were analyzed by scanning electron microscope (SEM), and the corresponding laws between micro damage devel-opment and macro mechanical behavior under different loading conditions were revealed by cluster analysis of acoustic emission (AE) signals. The test results show that the micro damage caused by tensile and shear stress components promote each other. The macro mechanical behavior of SiCf/SiC-CMC under complex loading is controlled by basic micro damage forms such as matrix cracking, interface debonding and fiber fracture. The tension-shear coupling load affects the evolution process of the basic damage forms, and then change the macro properties of SiCf/SiC-CMC.

Automated summary

This study experimentally analyzed the macroscopic mechanical behavior and coupling damage mechanism of 2D woven SiCf/SiC ceramic matrix composites (CMC) prepared by chemical vapor infiltration (CVI) process under tension-shear coupling load. It was found that the tensile modulus and proportional limit of SiCf/SiC-CMC had no significant difference with the increase of off-axis angle, while the failure strength decreased. Microscopic analysis using scanning electron microscope (SEM) and cluster analysis of acoustic emission (AE) signals revealed the main damage types and their relationship with macro mechanical behavior under different loading conditions. It was observed that the tension-shear coupling load affected the evolution process of basic damage forms and subsequently changed the macro properties of SiCf/SiC-CMC.