1：Experimental Design and Method Selection:

The study used a THz-TDS imaging system in reflection and transmission modes to detect defects such as debonding, delamination, and multi-delamination in various aircraft sandwich composites. Theoretical models for optical parameters (refractive index, absorption coefficient) were employed based on time-domain and frequency-domain data analysis.

2：Sample Selection and Data Sources:

Specimens included GF A-sandwich panels with PMI foam core, GF C-sandwich panels with Nomex honeycomb core, and GF sheet-to-sheet cementing structure, prepared with artificial defects using ultrathin double-layer Teflon inserts. Data were acquired through THz scanning.

3：List of Experimental Equipment and Materials:

Equipment included a FiCO REV

4：0 fiber coupled THz time-domain spectrometer, femtosecond laser system, XY-stage, and PMMA chamber. Materials involved GFRP composites, PMI foam, Nomex honeycomb, epoxy resin adhesive film, and Teflon inserts. Experimental Procedures and Operational Workflow:

The system was calibrated with air references. THz pulses were generated and detected in reflection or transmission modes, with scanning over defined areas. Time-domain waveforms were captured, and frequency-domain data were obtained via FFT. Image processing methods (wavelet-based fusion, multiscale edge representation) were applied to enhance defect visualization.

5：Data Analysis Methods:

Optical parameters were calculated using derived equations for refractive index and absorption coefficient. Defect sizes, locations, depths, and thicknesses were determined from time delay differences and imaging algorithms. Statistical analysis was not explicitly mentioned, but quantitative comparisons were made with actual values.