Nondestructive evaluation of aircraft composites using reflective terahertz time domain spectroscopy

Terahertz time domain spectroscopy in reflection configuration was assessed as a nondestructive evaluation technique for aircraft glass fiber composites. A technique for measuring the material properties of glass fiber composites using reflection geometry was demonstrated in addition to imaging of damaged glass fiber composites. Surface defects such as localized burn damage, puncture holes, and paint/composite removal were detected using amplitude and phase imaging methods. Hidden voids were also detected using the relative amplitude of the first Fabry–Perot reflection. The depths of discontinuities were then measured using a Fourier technique and then subtracting the incident pulse from the reflected pulse. Finally, nondestructive evaluation techniques for transmission and reflection configurations were compared.