复合材料冲击损伤高分辨率超声成像检测与损伤行为分析

High-resolution Ultrasonic Imaging Evaluation and Behavior Analysis of Impact Damages in Composites

冲击损伤是复合材料结构易产生的一种危害性缺陷,针对碳纤维复合材料层压结构特点,分析脉冲超声波在复合材料中的反射特性,当能减小入射声波脉冲的时域占宽,提高其品质,可显著改善超声检测表面盲区和纵向分辨率。利用入射声波在冲击损伤区形成的反射信号及其渡越时间可确定冲击损伤的深度和大小。研究采用高分辨率脉冲超声B扫描和层深C扫描(T扫描)成像方法,可揭示复合材料内部冲击损伤及其大小与沿厚度方向的分布特征,进行复合材料冲击损伤量化评估与损伤行为可视化分析。试验结果表明,在入射脉冲单周脉冲特性条件下,当来自复合材料缺陷的回波信号的渡越时间达到入射声波脉冲时域占宽的一半左右时,即可清晰地提取到时域可分辨的缺陷回波信号,使超声检测表面盲区和纵向分辨率达到单个复合材料预浸料铺层的厚度,约0.13 mm。利用超声断面B扫描成像,可以形象地再现复合材料中冲击损伤的断面分布与扩展情况以及损伤的深度等确切信息。采用超声T扫描成像,则可以直观地再现冲击损伤在复合材料铺层方向的分布及其损伤区域(面积)等定量信息。二者的结合则为揭示复合材料冲击损伤的3D分布及其特征提供一种超声成像检测量化评估和损伤行为可视化分析方法。

Impact damage is a harmful defect, which is easily induced in composite structures during manufacturing and in-service. Impulse ultrasonic wave reflections in carbon fiber-reinforced composites （CFRC） are analyzed. Ultrasonic surface dead-zone （USDZ） and lateral resolution （LR） can be improved markedly when time-widlh of probe pulse （TWOPP） is decreased reasonably and its property is polished appropriately. The datum about depth and size of impact damages in CFRC body can be extracted from ultrasonic reflected signals at damages and their time-of-flight （TOF）. B-scan and C-scan in depth （or T-scan） imaging techniques based on the investigated high-resolution ultrasonic method are employed to explore the details and to carry out visualized inspection and quantitative evaluation of impact damages induced in CFRC laminated specimens. Experimental results have shown that time-resolved reflections resulted from defects nearby CFRC specimen surface can be obtained distinctly when their TOFs are close to the half of TWOPP and probe pulse has a single duration in time domain. In this case, the USDZ and LR can be approximately reached to the thickness of a single pre-preg ply of CFRC laminate, i.e., 0.13 mm. The distribution and development as well as depth of impact damages in cross-section of the CFRC laminated specimens can be seen well by using serials of B-scan imaging technique.The quantitative information about impact damage zone and size along layup direction of CFRC laminated specimens can be excavated and determined exactly by using ultrasonic T-scan imaging method. The combination of the two kinds of imaging methods provides a powerful imaging and quantitative approaches for evaluation of impact damage as well as visual exploring 3D behavior of impact damage in CFRC laminates.