基于声发射信号的不同密度C/SiC复合材料损伤演化

对密度为1.65 g/cm3、1.75 g/cm3和1.85 g/cm3的平纹编织C/SiC复合材料进行单向拉伸试验，获得材料的基本力学性能。采用声发射技术对材料在单调拉伸试验全程下的损伤信号进行监测，并对采用Wavelet小波方法降噪后的声发射信号进行特征参数分析和K-聚类分析。结合SEM图像分析发现材料密度的不同使材料损伤模式、损伤演化过程及破坏模式存在差异。根据损伤模式和声发射事件分布特征将试验声发射信号进行分类分析，研究不同密度材料的损伤模式和损伤演化机制，发现:随着密度增大，不同损伤模式发生的起始应力水平、相对时间及频数逐渐增大。分析得出结论:材料密度通过影响基体损伤程度和损伤分布区域以及界面性能改变材料力学性能。 

Damage evolution of C/SiC composite materials with different densities based on acoustic emission signal analysis

The braided C/SiC composites with density of 1.65 g/cm³, 1.75 g/cm³ and 1.85 g/cm³ were tested to obtain the basic mechanical properties. The acoustic emission system was used to monitor the damage signals of the monotonic tensile test, and the characteristic parameter and K-cluster analysis of the acoustic emission signals after the noise reduction using wavelet method were analyzed. The difference of material density between the material damage mode, damage evolution process and failure modes was found by the analysis of SEM image. According to the distribution characteristics of the damage mode and acoustic emission events, the experimental acoustic emission signals were classified and analyzed, and the damage modes and damage evolution mechanisms of different density materials were studied, and the stress level, relative time and frequency of different damage modes are gradually increased with the increase of density. It is concluded that the material density can change the mechanical properties by influencing the damage degree and distribution area of matrix as well as the interfacial properties.