2D-C/SiC复合材料低温动态Z向压缩性能

Dynamic compressive properties of 2D-C/SiC composites' Z-direction in low temperature

采用Hopkinson压杆试验装置,对2D-C/SiC复合材料进行了低温条件下的Z向动态压缩性能试验研究,低温条件通过控制酒精和液氮的配比系数得到,通过改变波形整形器几何尺寸的方法来实现恒应变率加载,以得到准确、可信的试验结果。试验结果表明:由于复合材料内部含有大量初始微缺陷,2D-C/SiC复合材料在低温动态加载条件下呈现伪塑性行为,其破坏时并未表现出典型的脆性破坏,而是在应力达到压缩强度时出现了显著的应变软化现象,在经历了较大的变形后才最终破坏。随着温度的降低,复合材料的动态Z向压缩强度增加,但失效应变减小。2D-C/SiC复合材料在低温环境下,其内部纤维和基体之间界面结合力增强,同时强的界面结合力可以导致高的压缩强度。

The tests for dynamic compressive properties of 2D-C/SiC composites' Z-direction were performed in low temperature circumstance by using the SHPB system.The low temperature was made by controlling the ratio of coefficients between alcohol and liquid nitrogen to be obtained.The key issue to apply high strain rates to the 2D-C/SiC was to design the geometrical size of the shaper in the SHPB system.The test results of the dynamic loading were successful.Results indicate that 2D-C/SiC composite material show pseudo-plastic behavior at dynamic loading conditions in low temperature circumstance owing to a lot of internal microcracks in the initial composite material,so it does not exhibit typical brittle failure when the composites were destroyed,but it shows the strain softening phenomenon significantly when the stress reaches the compressive strength of the composites,and the specimens have experienced a large deformation before destruction.As the temperature decreases,the dynamic compressive strength of composites' Z-direction increases,but the failure strain decreases.At low temperatures,the interface between the internal fiber and matrix in the 2D-C/SiC composites enhances the binding force of the interface,and the more strength interfacial force can lead to a more strength high compression.