Terahertz Spectroscopic Characterization and Thickness Evaluation of Internal Delamination Defects in GFRP Composites

Chinese Journal of Mechanical Engineering

Original Article

Shuncong Zhong¹  Bing Wang¹  Walter Nsengiyumva¹  Manting Luo² 

[1] Fujian Provincial Key Laboratory of Terahertz Functional Devices and Intelligent Sensing, School of Mechanical Engineering and Automation, Fuzhou University, 350108, Fuzhou, China;Institute of Precision Instrument and Intelligent Measurement & Control, Fuzhou University, 350108, Fuzhou, P. R. China;School of Mechanical and Electrical Engineering, Putian University, 351100, Putian, China;

关键词: Glass-fiber-reinforced polymer-matrix (GFRP) composites;    Terahertz time-domain spectroscopy (THz-TDS);    Nondestructive testing and evaluation (NDT&E);    Stationary wavelet transform (SWT);    Thickness evaluation;    Delamination defects;   

DOI  :  10.1186/s10033-022-00829-7

 received in 2022-02-19, accepted in 2022-12-18,  发布年份 2022

来源: Springer

【 摘 要 】

The use of terahertz time-domain spectroscopy (THz-TDS) for the nondestructive testing and evaluation (NDT&E) of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials. In this study, the THz-TDS system is used to detect, localize and evaluate hidden multi-delamination defects (i.e., a three-level multi-delamination system) in multilayered GFRP composite laminates. To obtain accurate results, a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight (TOF) signals. The thickness and location of each delamination defect in the z-direction (i.e., through-the-thickness direction) are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates. A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712% relative error, while the relative error of the non-de-noised signals reaches 16.388%. Also, the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches. The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS. Also, the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.

【 授权许可】

CC BY   
© The Author(s) 2023

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