Accession Number : ADA491327


Title :   Nondestructive Evaluation of Aircraft Composites Using Terahertz Time Domain Spectroscopy


Descriptive Note : Doctoral thesis


Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT


Personal Author(s) : Stoik, Christopher D


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a491327.pdf


Report Date : 10 Dec 2008


Pagination or Media Count : 161


Abstract : Terahertz (THz) time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Material properties of glass fiber composite were measured using both transmission and reflection configuration. The interaction of THz with a glass fiber composite was then analyzed, including the effects of scattering, absorption, and the index of refraction, as well as effective medium approximations. THz TDS, in both transmission and reflection configuration, was used to study composite damage, including voids, delaminations, mechanical damage, and heat damage. Measurement of the material properties on samples with localized heat damage showed that burning did not change the refractive index or absorption coefficient noticeably; however, material blistering was detected. Voids were located by THz TDS transmission and reflection imaging using amplitude and phase techniques. The depth of delaminations was measured via the timing of Fabry-Perot reflections after the mail pulse. Evidence of bending stress damage and simulated hidden cracks was also detected with terahertz imaging.


Descriptors :   *COMPOSITE MATERIALS , *MILITARY AIRCRAFT , *NONDESTRUCTIVE TESTING , REFRACTIVE INDEX , THESES , GLASS FIBERS , FABRY PEROT INTERFEROMETERS , TIME DOMAIN , ABSORPTION COEFFICIENTS , SPECTROSCOPY , SCATTERING , CRACKS


Subject Categories : Aircraft
      Coatings, Colorants and Finishes
      Atomic and Molecular Physics and Spectroscopy


Distribution Statement : APPROVED FOR PUBLIC RELEASE