复合材料蒙皮–加强筋接头缺陷单脉冲超声表征与评估

Characterisation and Evaluation of Defects in Composite Skin–Rib Joint Using Mono-Pulse Ultrasonic Method

蒙皮–加强筋接头是一种非常重要的碳纤维复合材料壁板结构连接形式,因蒙皮–加强筋接头几何外形、内部铺层、缺陷行为与取向等都很复杂,蒙皮–加强筋接头区的缺陷表征、检测与评估一直是业内关注的技术难点和焦点。本文提出了一种利用单脉冲超声波在蒙皮–加强筋接头产生的反射行为的缺陷表征与评估新方法,试验结果表明,单脉冲超声波在复合材料蒙皮–加强筋接头区产生的反射信号具有非常好的时域可分辨性,回波信号达到1个脉冲周期时,表面检测盲区可以达到单个铺层厚度(约0.125 mm),可对分层、脱黏、胶接层、树脂层以及连接接头铺层变化等进行超声表征和评估,检出缺陷大小的最小偏差为0.0 mm,最大偏差为1.0 mm;检出分层深度定位偏差小于0.5个复合材料预浸料铺层。从而为复合材料蒙皮–加强筋接头提供了一种非常有效的超声表征与评估新方法,已经取得了很好的实际检测应用效果。

The skin–rib joint is a very important form in carbon fiber composite panels.Because of the complex in geometric structure,internal layer,defect behavior and orientation of fibers therein,defect characterisation,detection and evaluation have been the technical difficulties and focus in their applications.In this paper,a new method for defect characterization and evaluation is proposed using mono-pulse ultrasonic(MU)wave.The experimental results show that the echo signals resulted from the skin–rib joints have very good time-domain resolution under MU reflection condition.When echo signal is close to one pulse cycle,the ultrasonic surface detection dead zone can reach a single layer thickness(about 0.125 mm).Delamination,disbanding,adhesive layer,resin layer and internal layer variation in the skin–rib joints can be characterized,detected and evaluated.The minimum deviation of detected defect is close to 0.0 mm,and the maximum deviation is about 1.0 mm compared with their designed sizes.The depth positioning deviation of detected defect is less than 0.5 prepreg ply thickness.It provides a very effective ultrasonic characterisation and evaluation method for the composite panels.Good practical application has been obtained.