混编碳纤维与碳化硅纤维增强SiC基复合材料的制备及刚度预测

发布时间：2018-10-07 20:58

【摘要】：连续纤维增强SiC基复合材料具有较高的比强度和比模量、低密度等特性,同时拥有耐高温、抗氧化等优异性能,已广泛应用于航空航天、汽车及核工业等领域。混杂纤维复合材料不仅保留着单种纤维增强复合材料的优点,更具有单种纤维增强复合材料不能实现的效果,在力学性能、摩擦性能、热性能等方面展示出独特性。但是,混杂纤维复合材料在陶瓷基复合材料中的研究和应用鲜有报道。本文开展了2D混编碳纤维和碳化硅纤维增强SiC基复合材料刚度预测;制备层间混编碳纤维和碳化硅纤维增强SiC基复合材料,对所制备的混编复合材料拉伸性能和弯曲性能进行了测试表征及分析;且制备纯SiC基体,测量其工程常数应用于复合材料刚度计算;最后,对比其拉伸模量的计算值和实验值。通过采用蛋白发泡工艺制备SiC基体骨架,以低分子液态聚碳硅烷(LPVCS)为先驱体,采用PIP工艺制备与复合材料中基体类似的纯SiC基体。采用压汞法对制备过程中SiC基体的密度、孔隙率和孔隙分布进行分析,SiC基体的最终密度为2.6g/cm3,孔隙率为23.6%。采用弯曲共振法测量SiC基体工程常数,SiC基体的杨氏模量为36.6GPa,剪切模量为6.1GPa,泊松比为1.9。对2D混编预制件的混编方式进行设计,提出合理的混编复合材料单胞模型;根据不同的单胞模型,对单胞内纤维的空间形状进行分析;考虑陶瓷基复合材料界面层对其力学性能的影响,运用平均刚度法对混编复合材料刚度进行预测。通过所制备的混编复合材料拉伸模量预测值和实验值的对比发现,例如,碳纤维与碳化硅纤维层数比为1:5时,模量计算值和预测值分别为47.5MPa和40.4MPa,在误差和实验可能存在的原因内预测模型较为合理。通过混编复合材料的弯曲和拉伸性能进行测试表征发现,碳纤维与碳化硅纤维层数比为1:5的混编复合材料弯曲和拉伸强度分别为572.1MPa和111.1MPa,SiC/SiC复合材料的弯曲和拉伸强度分别为512.6MPa和102.9MPa,说明少量碳纤维的加入使SiC/SiC复合材料的强度得到了提高。观察复合材料应力-应变曲线发现,混编复合材料在断裂过程中出现多次断裂。
[Abstract]:Continuous fiber reinforced SiC matrix composites have been widely used in aerospace, automobile and nuclear industry because of their high specific strength and modulus, low density, high temperature resistance, oxidation resistance and so on. Hybrid fiber composites not only retain the advantages of single fiber reinforced composites, but also have effects that can not be realized by single fiber reinforced composites. The hybrid fiber composites exhibit unique mechanical properties, friction properties and thermal properties. However, the research and application of hybrid fiber composites in ceramic matrix composites are rarely reported. In this paper, the stiffness prediction of 2D carbon fiber and silicon carbide fiber reinforced SiC matrix composites was carried out, and interlaminar carbon fiber and silicon carbide fiber reinforced SiC matrix composites were prepared. The tensile properties and flexural properties of the composites were tested and analyzed, and the pure SiC matrix was prepared. The engineering constants were measured and applied to the stiffness calculation of the composites. Finally, the calculated and experimental values of the tensile modulus of the composites were compared. The matrix skeleton of SiC was prepared by protein foaming process. The pure SiC matrix similar to the matrix in the composites was prepared by PIP process using low molecular weight liquid polycarbosilane (LPVCS) as precursor. The density, porosity and pore distribution of SiC matrix were analyzed by mercury injection method. The final density and porosity of sic matrix were 2.6g / cm ~ 3 and 23.6g 路cm ~ (-3), respectively. The Young's modulus, shear modulus and Poisson's ratio of SiC matrix engineering constant and sic matrix are 36.6 GPA, 6.1 GPA and 1.9, respectively, measured by bending resonance method. In this paper, the blending mode of 2D preforms is designed, and a reasonable unit cell model of composite material is proposed, and the spatial shape of fiber in the cell is analyzed according to different unit cell models. Considering the influence of interfacial layer on mechanical properties of ceramic matrix composites, the average stiffness method was used to predict the stiffness of composite materials. By comparing the predicted and experimental values of tensile modulus of the prepared composite, for example, when the ratio of layers of carbon fiber to silicon carbide fiber is 1:5, The calculated and predicted modulus values are 47.5MPa and 40.4 MPa, respectively. The prediction model is reasonable within the error and the possible reasons of the experiment. The bending and tensile properties of the composites were measured and characterized. The flexural and tensile strength of the composite with 1:5 ratio of carbon fiber to silicon carbide fiber is 572.1MPa and 111.1 MPA sic / sic respectively. The bending and tensile strength of the composites are 512.6MPa and 102.9 MPa, respectively, indicating that the strength of SiC/SiC composites is improved by adding a small amount of carbon fiber. By observing the stress-strain curves of composite materials, it is found that multiple fracture occurs in the fracture process of hybrid composites.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332;TQ342.742

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