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采用化学气相渗透法制备了2维和2.5维碳纤维增强碳化硅(carbon-fiber-reinforced silicon carbide,C/SiC)复合材料,沿经纱(纵向)和纬纱(横向)2个方向对2种复合材料进行了室温拉伸性能测试,并从预制体结构和原始缺陷分布的角度对比分析了两者力学性能之间的差异。结果表明:两种C/SiC复合材料均表现出明显的非线性力学行为,在经纱方向和纬纱方向上,2维C/SiC复合材料力学性能表现为各向同性,而2.5维C/SiC复合材料力学性能则表现出明显的各向异性:经纱方向上2.5维C/SiC复合材料的拉伸强度和拉伸模量(326MPa,153 GPa)均高于2维C/SiC复合材料的(245 MPa,96GPa),纬纱方向上的(145 MPa,62GPa)均低于2维C/SiC复合材料的(239MPa,90GPa)。两种复合材料的拉伸断裂行为均表现为典型的韧性断裂,并伴有大量的纤维拔出。两种复合材料中纱线断裂均呈现出多级台阶式断裂方式,但其断裂位置并不相同。2.5维C/SiC复合材料中由于经纱路径近似于正弦波,弯曲程度较大,在纱线交叉点处造成明显的应力集中,因此经纱多在纱线交叉点处断裂;而纬纱由于其路径近乎直线,应力集中现象不明显,因此纬纱断裂位置呈随机分布。2维C/SiC复合材料中经纱和纬纱由于其路径类似于2.5维C/SiC复合材料中的经纱,因此其断裂位置也多在纱线交叉点处。微观结构观察表明不同的编织结构是造成两种复合材料在不同方向上力学性能差异的主要原因。
Two-dimensional and two-dimensional carbon-fiber-reinforced silicon carbide (C / SiC) composites were prepared by chemical vapor infiltration method. Two kinds of composites were prepared along both warp (longitudinal) and weft The tensile properties at room temperature were tested. The differences between the mechanical properties of the two were compared between the preform structure and the original defect distribution. The results show that both C / SiC composites show obvious nonlinear mechanical behavior. The mechanical properties of 2-dimensional C / SiC composites are isotropic in both warp direction and weft direction, while 2.5-dimensional C / SiC composites The mechanical properties of the composites show obvious anisotropy: the tensile strength and tensile modulus (326MPa, 153 GPa) of 2.5-dimensional C / SiC composites in warp direction are both higher than those of 2-dimensional C / SiC composites MPa, 96GPa) and weft direction (145 MPa, 62GPa) were lower than that of 2-dimensional C / SiC composites (239MPa, 90GPa). Tensile fracture behavior of both composites showed typical ductile fracture accompanied by a large amount of fiber pull-out. In both composites, the fracture of the yarn shows a multi-step stepped fracture mode, but its fracture location is not the same. In the 2.5-dimensional C / SiC composites, because the warp yarn path is similar to the sine wave, the bending degree is larger and causes obvious stress concentration at the yarn crossing point. Therefore, the warp yarn breaks at the yarn crossing point. Straight line, the phenomenon of stress concentration is not obvious, so the location of weft yarn was randomly distributed. The warp and weft yarns in 2-dimensional C / SiC composites also have more fracture locations at the intersection of yarns due to their similar paths to the warp yarns in 2.5-dimensional C / SiC composites. The microstructure observation shows that different braided structures are the main reason for the difference of the mechanical properties of the two composites in different directions.