楔块耦合的碳纤维增强复合材料褶皱缺陷全聚焦成像

Total focusing imaging of wrinkle defects in carbon-fiber-reinforce-polymer composites based on wedge coupling

褶皱是碳纤维增强复合材料中最主要的缺陷类型之一,当使用超声相控阵对复合材料薄板进行检测时,由于采集系统非线性效应和电子串扰等干扰会引发盲区现象,掩盖了薄板内的褶皱信息。为削弱盲区影响,考虑在相控阵与复合材料薄板(小于10 mm)之间增加楔块,提出楔块耦合的最短路径射线追踪全聚焦方法。基于费马原理与斯涅耳定律,建立楔块耦合的多层介质超声波传播模型;制备含褶皱缺陷的碳纤维增强复合材料试样,搭建超声相控阵数据采集系统,采集全矩阵数据;将楔块耦合的最短路径射线追踪全聚焦方法和传统全聚焦方法的成像效果进行对比。结果表明,基于楔块耦合的最短路径射线追踪全聚焦方法能减小试样表面盲区深度,修正声时偏差,削弱盲区影响,恢复出试样内的褶皱缺陷。相比传统全聚焦方法,纤维褶皱长度、褶皱顶部高度、褶皱角度这3个参数表征的精准程度分别提高了5.9%、4.1%、4.2%。该文为碳纤维增强复合材料薄板褶皱缺陷的检测提供了新思路。

Wrinkles are one of the main types of defects in carbon-fiber-reinforce-polymer(CFRP)composites materials.When using ultrasonic phased array for wrinkle defects detection,blind zones phenomena are caused by interference,such as non-linear effects and electronic crosstalk in the acquisition system,which conceal the wrinkle information inside the thin plate.To reduce the impact of blind zones,an approach is proposed to add a wedge between the phased array and the composite material thin plate(less than 10 mm),and a shortest path ray tracing total focusing method coupled with the wedge is presented.Based on Fermat’s principle and Snell’s law,a multi-layered medium ultrasonic wave propagation model with the wedge is established.CFRP material samples with wrinkle defects are prepared,and a phased array ultrasonic data acquisition system is constructed to collect full matrix data.The imaging effects of the shortest path ray tracing total focusing method coupled with the wedge and traditional total focusing method are compared.The results indicate that the shortest path ray tracing total focusing method coupled with the wedge can reduce the depth of the blind zones on the surface of the specimen,correct the acoustic time deviation,and weaken the impact of blind zones,and restore the wrinkle defects inside the sample.Compared to the traditional total focusing method,the accuracy of the three parameters characterizing fiber wrinkles,including wrinkle length,wrinkle top height,and wrinkle angle,is improved by 5.9%,4.1%,and 4.2%,respectively.This paper provides a new approach for the detection of wrinkle defects in CFRP material thin plates.