面向航空复合材料结构的激光超声无损检测技术

Non-Destructive Testing for Aerospace Composite Structures Using Laser Ultrasonic Technique

针对层合形式含曲面的航空结构大面积检测难题,基于非接触式扫描的激光超声检测技术得到了广泛的研究与关注。该技术采用脉冲式激光激励结构中的超声波,获取超声波在检测区域内的传播数据,通过分析超声波传播特征参数的变化,实现结构损伤和性能的评估。围绕使用日益广泛的航空复合材料结构,从结构脱粘损伤的识别、疲劳损伤累积的表征和疲劳剩余寿命的预测3个方面,介绍了激光超声检测技术的相关研究进展。首先,以层合结构为例,研究了脱粘损伤对超声波传播的影响,通过能量、波数等特征参数提取,实现了脱粘损伤成像;其次,研究了纤维增强复合材料中基体裂纹累积对超声波模态转换效应的影响规律,通过量化模态转换效应对基体裂纹密度进行表征;最后,建立了基于损伤形式的复合材料疲劳演化模型,采用贝叶斯模型平均和激光超声的波速测量,完成了剩余疲劳寿命的预测,为未来激光超声检测在航空复合材料中的应用提供了参考。

Aimed at solving the problem of large-area detection for aerospace laminated structures with curved surfaces,laser ultrasonic technique with non-contact measurement has attracted more and more attention.By using pulsed laser to generate the ultrasonic waves in the structures,the wave-field data can be obtained.Through analyzing the characteristics of ultrasonic wave propagation,the structural damage detection and mechanical property identification can be achieved.Focused on the widely used aerospace composite structures,this paper presents the research progress on three aspects:debonding damage detection,damage accumulation characterization and fatigue life prediction.Taking laminated composite structures as an example,the influence of debonding damage on ultrasonic wave propagation is studied.By extracting the damage index,such as wave energy and wave number,the debonding damage can be visualized.Then,the influence of matrix crack accumulation in fiber reinforced polymer on mode conversion is investigated.By defining a mode-to-mode ratio,the density of matrix cracks can be characterized.Finally,a micro-damage based fatigue evolvement model for composites is established.Through Bayesian model averaging and wave velocity measurement using laser ultrasonic technique,the fatigue life of composites can be predicted,providing foundation for non-destructive testing in aerospace composite structures.