P_yC/SiC/TaC界面对三维细编C_f/C复合材料力学性能的影响

Influences of P_yC/SiC/TaC Interfaces on Mechanical Properties of 3D Fine-woven Punctured C_f/C Composites

采用等温气相沉积方法制备了一种含PyC/SiC/TaC界面的炭/炭复合材料,采用偏光显微镜、X射线衍射和扫描电镜分析了材料的结构和断裂特点,采用单轴拉伸和三点弯曲方法研究了PyC/SiC/TaC界面对炭/炭复合材料力学性能的影响。金相和XRD表明热解炭界面是各向同性炭,TaC界面是NaCl型立方结构,SiC的结构以立方β-SiC为主,有少量的10H-SiC结构。TaC/SiC纤维界面能显著提高复合材料的拉伸、弯曲性能以及Z向压缩性能。整体密度为1.89 g/cm3时,含界面炭/炭材料的抗弯强度达375 MPa,约为无界面材料的4倍,同时材料整体密度的增加也能显著改善其力学性能。分析表明材料总体呈非线性脆断,有一定的假塑性行为。压缩载荷作用下Z向和XY向都为与受力方向成45°的剪切型破坏。

The 3D fine-woven punctured Cf/C-（PyC/SiC/TaC） composites,composed of PyC/SiC/TaC interfaces and pyrocarbon（PyC） matrix,were synthesized by isothermal chemical vapor infiltration（ICVI） methods.The structure and fracture characteristics of these composites have been examined by polarized light microscopy（PLM）,scanning electron microscopy（SEM） and X-ray diffraction（XRD）.The influences of PyC/SiC/TaC interfaces on the C/C composites were investigated by uniaxial tension and three-point bending methods.It was found that the PyC interface has isotropic（ISO） structure,and the TaC layer has NaCl-type cubic structure,while the SiC layer has few wurtzite type 10H-SiC besides β-SiC structure.The TaC/SiC fiber coating can greatly improve tensile,flexural and z-direction compressive properties of the composites.The maximum of flexural strength are 375 MPa at density of 1.89 g/cm3,which are about three times higher than that of samples without TaC/SiC fiber coating.The mechanical properties can be improved obviously by the increase of bulk density of the composites as well.The analysis tells that the composite exhibits a nonlinear brittle failure,indicating a certain pseudoplastic behavior.Failure modes of the samples under compressive load along Z or XY direction present 45° shear fracture.