Abstract-An Infrared-Induced Terahertz Imaging Modality for Foreign Insert Detection in A Glass Fiber-Skinned Lightweight Honeycomb Composite Panel

Hai Zhang,  Stefano Sfarra,   Ahmad Osman,   Klaus Szielasko,  Christopher Stumm,  Marc Genest,  Xavier Maldague

https://ieeexplore.ieee.org/document/8353417/

In this paper, terahertz time-domain spectroscopy (THz-TDS) is used for the first time to detect fabricated defects in a glass fiber-skinned lightweight honeycomb composite panel. A novel amplitude polynomial regression (APR) algorithm is proposed as a pre-processing method. This method segments the amplitude-frequency curves to simulate the heating and the cooling monotonic behavior as in infrared thermography. Then, the method of empirical orthogonal function (EOF) imaging is applied on the APR pre-processed data as a post-processing algorithm. Signal-to-noise ratio analysis is performed to verify the image improvement of the proposed APR-EOF modality from a quantitative point of view. Finally, the experimental results and the physical analysis show that THz is more suitable with respect to the detection of defects in glass fiber lightweight honeycomb composites.