Abstract

Terahertz (THz) time-domain spectroscopy was used to detect the artificially pre-embedded circular polytetrafluoroethylene (PTFE) slice defects at different depth (0.225–0.9 mm) in carbon-fiber-reinforced polymer composites. The THz reflectance peak-to-peak value, maximum value, and delay time in the time-domain waveform, and spectral characteristics in frequency domain of defects were analyzed. It was found that the defects in the specimen can be effectively distinguished in the frequency range of 0.16–2.0 THz by THz reflection imaging technology. With the increase of depth of the defects in the specimen, the peak-to-peak value and maximum value of THz signals show a linear attenuation, and the delay time increases accordingly. The analysis results of frequency-domain signals of the defects in specimens also confirm the accuracy of the former results. This technology exhibits potential applications in distinguishing and sorting the defects at different depths in a carbon-fiber composite, and can provide an important reference for nondestructive composite failure detection in this area.

中文翻译：

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通过太赫兹时域光谱无损检测碳纤维增强聚合物复合材料中的深度相关缺陷

摘要

太赫兹（THz）时域光谱用于检测碳纤维增强聚合物复合材料中不同深度（0.225-0.9 mm）的人工预埋圆形聚四氟乙烯（PTFE）切片缺陷。分析了时域波形中的太赫兹反射峰峰值、最大值和延迟时间，以及缺陷的频域频谱特征。发现通过太赫兹反射成像技术可以在0.16-2.0 THz频率范围内有效区分试样中的缺陷。随着试样缺陷深度的增加，太赫兹信号的峰峰值和最大值呈线性衰减，延迟时间相应增加。试样中缺陷的频域信号分析结果也证实了前一种结果的准确性。该技术在区分和分类碳纤维复合材料不同深度的缺陷方面具有潜在的应用价值，可为该领域的复合材料无损检测提供重要参考。