碳纤维增强环氧树脂复合材料螺栓连接结构在拉伸载荷下损伤过程的声发射分析

采用声发射技术对不同几何尺寸的碳纤维增强环氧树脂复合材料（CFRP）螺栓连接结构在静力载荷下破坏行为进行了试验研究，比较了不同几何构型下的连接结构的破坏行为与声发射信号之间的映射关系。采用声发射技术对结构损伤过程中的声发射信号进行全程采集与转换，结合CFRP螺栓结构的载荷-位移曲线和宏/细观破坏形貌，分析了幅值、熵曲线和Andrews曲线与破坏行为之间的关系。结果表明:挤压与剪切破坏试件的载荷-位移曲线均呈现出较明显的塑性特征。结构发生挤压和剪切破坏时，声发射信号以中幅值信号为主，并伴随少量高幅值信号；结构发生拉伸破坏时对应的幅值为中幅值信号。根据熵曲线特征将CFRP连接结构破坏过程分为四个阶段，在损伤演化阶段发生纤维断裂、分层等失效模式，在结构失效阶段以分层失效为主。基于Andrews曲线分析得到挤压和拉伸失效模式在损伤演化阶段会出现多种损伤类型，剪切失效模式在结构失效阶段会出现多种损伤类型。 

Acoustic emission analysis of carbon fiber reinforced polymer bolted joints damage process under tensile load

The acoustic emission(AE) technique was used to study the failure behavior of carbon fiber reinforced polymer(CFRP) bolted joints with different geometric sizes under static load, and the relationship between the damage behavior of the joint and the AE signal under different geometric was compared. The AE technology was used to collect and convert the AE in the process of structural damage, and the relationship between the amplitude, entropy curve, Andrews curve and the failure behavior was analyzed by combining the load-displacement curve of CFRP bolted and the macro/meso damage morphology. The results show that the load-displacement curves of bearing and shear failure specimens show obvious plastic characteristics. When the specimen is failure in bearing and shear, the AE is the medium amplitude signal, and a small number of high amplitude signals are accompanied. The medium amplitude signal occurs when the tensile damage happens. According to the characteristics of entropy curve, the failure process of CFRP joint is divided into four stages, and the failure modes such as fiber fracture and delamination occur at the stage of damage evolution, and the failure is dominated by delamination failure in the stage of structural failure. Based on the Andrews curve analysis, a variety of damage types are found in the failure evolution stage of the bearing and tensile failure modes, and many types of damage will appear in the failure stage of the shear failure mode.