碳纤维三维四向编织复合材料拉伸变形与损伤破坏行为

TENSILE DEFORMATION AND DAMAGE BEHAVIOR OF CARBON FIBER THREE DIMENSIONAL FOUR DIRECTIONAL BRAIDED COMPOSITES

为研究碳纤维三维编织复合材料的拉伸变形、损伤和破坏行为,采用声发射(Acoustic Emission,简称"AE")与数字图像相关(Digital Image Correlation,简称"DIC")互补技术,对碳纤维三维四向编织复合材料的声学衰减特性、拉伸变形与损伤破坏过程进行实时监测,动态获取对应的散斑图像与AE特征信号并进行相关计算和AE信号处理。结果表明:复合材料沿编织纱方向的衰减明显低于其他方向,断铅点与传感器的距离越远,衰减幅度越大;试件在加载前期,AE信号水平较低,位移场和应变场变化比较平稳,损伤累积阶段,AE相对能量逐渐升高,材料表现出明显的弹性变形特性,当载荷达到最大值时,拉伸方向和水平方向的位移和应变值均达到最大,试件失效断裂; AE与DIC综合检测与分析能较好地描述试件的损伤演化和破坏过程,为碳纤维三维编织复合材料的安全评价和健康监测提供借鉴。

In order to study the tensile deformation,damage and failure behavior of carbon fiber three-dimensional braided composites,the acoustic emission and digital image correlation complementary techniques are applied to the study of carbon fiber three-dimensional and four-directional braided composites.Meanwhile,acoustic attenuation characteristics,tensile deformation and damage destruction processes are monitored simultaneously.Besides,the corresponding speckle images and AE characteristic signals are acquired dynamically.Then the related calculations and AE signal processing are performed.The results show that the attenuation of the composite along the braiding yarn direction is significantly lower than that of other directions,and the farther the distance between the broken lead and the sensor is,the greater the attenuation amplitude is.At the early stage of the specimens loading,AE signal levers are a bit low and the displacement fields as well as strain fields change steadily.In the accumulation phase of damage,t he relative energy of AE increases gradually,and the material exhibits obvious elastic deformation characteristics.When the load reaches the maximum value,both the displacement and strain values in the tensile direction and the horizontal direction reach the maximum,and the specimen fails and fractures.The comprehensive monitoring and analysis of AE and DIC can better describe the damage evolution and destruction process of the specimen,and provide reference for the safety evaluation and health monitoring of carbon fiber three-dimensional braided composites.