预制体结构及界面对三维SiC/SiC复合材料拉伸性能的影响

为研究预制体结构及界面对三维编织SiC/SiC复合材料拉伸性能的影响，采用先驱体浸渍裂解法（PIP）分别制备了三维四向和三维五向SiC/SiC复合材料，并引入热解炭/碳化硅（PyC/SiC）复合界面层，进行拉伸性能测试和断口形貌观察。结果表明，三维五向SiC/SiC复合材料拉伸性能优于三维四向SiC/SiC复合材料，三维五向SiC/SiC复合材料的拉伸强度、模量和断裂应变分别是三维四向SiC/SiC复合材料的1.22倍、1.25倍、1.43倍，且比三维四向SiC/SiC复合材料具有更好的强度可靠性。这是由于三维五向SiC/SiC复合材料增加了受力方向的纤维含量，限制了纤维在外力作用下的转动和变形，起到定型和稳固作用。添加PyC/SiC复合界面层，三维五向SiC/SiC复合材料的拉伸强度、模量及断裂应变分别提高了21.7%、15.0%和11.0%。界面的存在可以保护纤维，调节纤维与基体之间的热应力，受力时诱使裂纹偏转和分叉，消耗能量，提高三维五向SiC/SiC复合材料的拉伸性能。 

Effects of preform structure and interface types on tensile properties of 3D-SiC/SiC composites

To investigate the effects of fiber directionality and interface types on the tensile properties, 3D 4-directional and 3D 5-directional braided SiC/SiC composites were prepared by polymer infiltration and pyrolysis (PIP) process, and combined interface of PyC/SiC composite was introduced to the braided SiC preform surface for modification. The results indicate that 3D 5-directional SiC/SiC composite shows great advantages in tensile properties over 3D 4-directional SiC/SiC composite. The tensile strength, modulus and fracture strain of 3D 5-directional SiC/SiC composite are respectively 1.22 times, 1.25 times and 1.43 times of the corresponding properties of the 3D 4-directional SiC/SiC composite. Furthermore, 3D 5-directional SiC/SiC composites have better strength reliability than that of 3D 4-directional SiC/SiC composite. This is due to the increase of fiber content in the stress direction of the 3D 5-directional SiC/SiC composites, which limits the rotation and deformation of the fiber under the external force, resulting in shaping and stabilizing. With the interface of PyC/SiC, the tensile strength, tensile modulus and fracture strain of 3D 5-directional SiC/SiC composite increase by 21.7%, 15.0% and 11.0%, respectively. The interface can protect the fiber and adjust the thermal stress between the fiber and the matrix, which can induce the deflection and bifurcation of cracks and consume energy, resulting in the improvement of tensile properties of the 3D 5-directional SiC/SiC composites.