Multilayer composites assembled flexibly with have important effect on the performance and safety of aircrafts. The nondestructive detection on the adhesion layer is an important index to evaluate the quality of aircraft assembly. Terahertz Time-Domain Spectroscopy (THz-TDS) is a newly developed spectroscopy technique based on femtosecond laser technology which currently applied to qualitative analysis as a means of security detection and material identification. Compared with the traditional tensile testing, the detection of defects in the adhesion layer could be nondestructive, visible, positioning and more accurate. The spectral analysis on the material to be assembled was done respectively. The testing model was established in accord with the extracted optical parameters. With the employment of a reflective THz-TDS device, X-Y spot scanning was done to obtain waveforms of every location on an assembled sample. Layered analysis was done by selecting region of interest in time domain waveforms. Conclusions of Time- Frequency spectrum analysis and scanning imaging performance are relatively satisfying through the experiments. The defects could be located and analyzed accurately and efficiently. The research reveals that THz-TDS (0.1THz~5THz) has good testing performance on the adhesion quality of multilayer composites.
Coating curing curve is one of the most important methods to reflect the coating curing properties. It is of great significance for the coating curing properties. In this paper, by using the reflective Terahertz (THz) time-domain spectroscope technique, the curing properties of coating with different thicknesses are studied. Three different parameters used for studying the properties of coating curing curve are proposed in this paper. They are respectively the differential time of flight, power spectrum and amplitude for reflective THz time-domain waveform. In this paper, two kinds of coating (with different thicknesses) curing properties curves are established and the relative errors from three parameter analysis methods are compared respectively. This study shows that the study on coating curing properties curves by using the power spectrum of reflective THz time-domain waveform is superior to the amplitude parameter method. But for the thick coating, the differential time of flight for the reflective THz time-domain waveform can also better reflect the coating curing properties.
According to nondestructive testing principle for the terahertz time domain spectroscopy Imaging, using digital image processing techniques, through Terahertz time-domain spectroscopy system collected images and two-dimensional datas and using a range of processing methods, including selecting regions of interest, contrast enhancement, edge detection, and defects being detected. In the paper, Matlab programming is been use to defect recognition of Terahertz, by figuring out the pixels to determine defects defect area and border length, roundness, diameter size. Through the experiment of the qualitative analysis and quantitative calculation of Matlab image processing, this method of detection of defects of geometric dimension of the sample to get a better result.