化学气相渗透2.5维C/SiC复合材料的拉伸性能

采用等温减压化学气相浸渗(isothermal low-pressure chemical vapor infiltration,ILCVI)工艺制备了在厚度方向上具有纤维增强的2.5维(2.5 dimensional,2.5D)碳纤维增强碳化硅多层陶瓷基复合材料,从而使一端封口的防热结构部件的制备成为可能.ILCVI致密化后,复合材料的密度、孔隙率分别为1.95～2.1 g/cm3和16.5%～18%.沿经纱和纬纱两个方向对2.5D C/SiC复合材料进行室温拉伸实验.结果表明:复合材料在纵向和横向的拉伸应力-应变均表现为明显的非线性行为.复合材料具有较高的面内拉伸性能,纵横向的拉伸强度分别为326MPa和145MPa,断裂应变分别为0.697%和0.705%.复合材料的拉伸断裂为典型的韧性断裂,经纱和纬纱的断裂都表现为纤维的多级台阶式断裂以及纤维的大量拔出.

TENSILE PROPERTIES FOR 2.5 DIMENSIONAL C/SiC COMPOSITES FABRICATED BY CHEMICAL VAPOR INFILTRATION

Multi-layer 2.5 dimensional carbon fiber reinforced silicon carbide (2.5D C/SiC) ceramic matrix composites with through-thickness reinforcements were fabricated by the isothermal low-pressure chemical vapor infiltration (ILCVI) process; thereby it is possible to manufacture the thermostructural components with one closed end. After the ILCVI densification, the resulting composites have an open porosity of 16.5%-18% and a bulk density of 1.95-2.1 g/cm3, respectively. Tensile tests for monotonic loading parallel to the warp and weft directions were carried out at room temperature. The results show that the tensile stress-strain curves of 2.5 D C/SiC composite in both loading directions exhibit largely nonlinear behavior. The composites studied have higher in-plane tensile properties, with the tensile strength of 326 MPa in the warp direction and of 145 MPa in the weft direction, and the failure strain of 0.697% in the warp direction and of 0.705% in the weft direction. Observation of scanning electron microscope photographs reveal that the failure of the composites exhibits multiple yarn fracture, and the fracture of yarns demonstrates multi-step fiber fracture and extensive fiber pullout.