利用非线性超声和声发射检测技术对T700型碳纤维复合材料加卸载试验过程中的损伤变化过程进行了研究。重点分析了试件不同载荷阶段的超声非线性系数的演化规律，并结合声发射特征参量分析了Felicity比，将Felicity比和非线性系数变化曲线与不同加载阶段的对应关系相互验证。试验结果表明，超声非线性系数对T700型碳纤维复合材料损伤有较高的敏感性，通过其时域经历能反映出损伤的动态变化规律，且与声发射Felicity比有较好的一致性，因此可以将超声非线性系数作为评价静拉伸试验过程中损伤严重性的新方法。

In this paper,nonlinear ultrasonic and acoustic emission detection technology were used to study the damaging progress of T700 carbon fiber composite material under loading and unloading experiments. The evolution of ultrasonic nonlinear coefficients in different loading stages of the specimen was analyzed. Combined with acoustic emission characteristic parameter analysis and Felicity ratio, the correspondence relationship between change curves of Felicity ratio and nonlinear coefficient at different loading stages was verified. The results show that,ultrasonic nonlinear coefficient is highly sensitive to damage of T700 carbon fiber composites, which can reflect the dynamic change law of damage through its time domain experience. And it is in better agreement with Felicity ratio of the acoustic emission. Therefore, the ultrasonic nonlinear coefficient can be used as a new method to evaluate the damage severity in the process of static tensile test.