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采用声发射平均频率和相对能量以及幅值识别了3D C/SiC复合材料的拉伸损伤模式,探讨了拉伸加卸载过程中材料的费利西蒂(Felicity)效应。通过分析具有不同拉伸性能试样的损伤过程,研究了不同损伤模式的时间分布特征对材料拉伸性能的影响关系。分析结果表明,3D C/SiC复合材料中基本不存在凯瑟(Kaiser)效应,Felicity比随着应力水平的升高而降低,相对应力水平高于65%时出现突降。3D C/SiC复合材料高性能的决定性因素不是声发射波击总数,而是高幅高能量信号发生的时间和次数。在加载前期(应变<0.15%)损伤较少是材料高强度的必要条件,纤维簇断裂在加载中后期的分散分布有利于提高拉伸强度。
The tensile damage modes of 3D C / SiC composites were identified by the average acoustic emission frequency, relative energy and amplitude, and the Felicity effect of the materials during tensile loading and unloading was also discussed. By analyzing the damage process of specimens with different tensile properties, the relationship between the time distribution characteristics of different damage modes and the tensile properties of the materials was studied. The results show that there is almost no Kaiser effect in the 3D C / SiC composites, and the Felicity ratio decreases with the increase of the stress level. When the relative stress level is higher than 65%, the sudden drop occurs. The decisive factor for the high performance of 3D C / SiC composites is not the total number of acoustic emission strikes but the timing and number of high-amplitude high-energy signals. Pre-loading (strain <0.15%) less damage is a necessary condition for the high strength of the material. The dispersion of fiber tufts during the middle and late loading will be helpful to improve the tensile strength.