By using axial and off-axis loading tests with off-axis angle as 45°, the tensile, compressive and in-plane shear stress-strain behaviors along the fiber bundles directions of a 2D-SiC/SiC composite were obtained, and the damage coupling mechanical behaviors of composite under combined stress condition were studied. The results show that the initial stress levels for the damage coupling mechanical behaviors of composite under 45° off-axis tensile and compressive loading conditions are 40MPa and -110MPa, separately. Under combined stress conditions, there exists obvious mutual acceleration between the tensile and the in-plane shear damage evolutions in the fibre bundles directions of composite, and the in-plane shear damage has accelerative effect on the compressive damage evolution, but the in-plane shear damage evolution is suppressed by compressive stress components obviously. These coupling effects become more significant with increasing stress level. The SEM (scanning electron microscope) pictures of fractured surfaces on off-axis loading specimens indicate that, in the fiber bundles directions, the mutual effects between the three stress components and the cracking evolutions of the three kinds of matrix cracks (oriented at 0°, 90° and 45°) are the main micro-damage mechanisms for the damage coupling mechanical behaviors of 2D-SiC/SiC composite under combined stress conditions.
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