碳纤维复合材料不同深度缺陷的太赫兹检测研究

Research on THz detection of CFRP with different depth defects

太赫兹(THz)无损检测技术具有非破坏性、非电离和非接触的优点,在航空航天领域纤维增强复合材料无损检测中得到了较快的发展和应用。在碳纤维复合材料层合板的4个不同深度(0.225、0.450、0.675、0.900 mm)插入聚四氟乙烯作为人工缺陷,采用太赫兹时域光谱和成像系统对其进行成像和光谱分析,探讨太赫兹波辐射下缺陷的成像效果和光谱特性。研究结果发现,在0.25~2.0 THz频率范围内,太赫兹反射成像可以成功检测出碳纤维复合材料中不同深度缺陷:随着缺陷深度的增加,太赫兹频域成像信号和光谱信号随缺陷深度线性增大,吸收系数成像信号和光谱信号随缺陷深度线性减小;随着频率的增加,缺陷的功率谱密度先增大后减小,吸收系数缓慢增大。该结果可以为碳纤维复合材料缺陷深度的可视化和定量化分析提供参考依据。

Terahertz(THz) non-destructive testing technology has the advantages of non-destructive, non-ionizing and non-contact, and has been rapidly developed and applied in the non-destructive testing of fiber-reinforced composite materials in the aeronautics and astronautics field. PTFE was inserted into 4 different depths(0.225, 0.450, 0.675, 0.900 mm) of carbon fiber composite laminates as artificial defects, and the terahertz time-domain spectroscopy and imaging system was used to image and spectrally analyze it, discuss the imaging effects and spectral properties of defects under terahertz radiation. The results of the study show that in the frequency band of 0.25~2.0 THz, terahertz reflection imaging can successfully detect different depths defects in carbon fiber composites, the terahertz frequency imaging signal and spectral signal linear increased with the defect depth increment, the absorption coefficient imaging signal and spectral signal linear decreased with the defect depth increment, and with the increase of frequency, the power spectral density of the defect firstly increment and then decrement, and the absorption coefficient slowly increases. The results can provide a reference for the visualization and quantitative analysis of unknown depth defects in carbon fiber composites.