Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

3D non-destructive imaging of punctures in polyethylene composite armor by THz time domain spectroscopy

: Palka, N.; Panowicz, R.; Ospald, F.; Beigang, R.


Journal of infrared, millimeter, and terahertz waves 36 (2015), Nr.8, S.770-788
ISSN: 1866-6892
ISSN: 1866-6906
Fraunhofer IPM ()

An ultra-high molecular weight polyethylene composite sample totally punctured by a projectile was examined by THz TDS raster scanning method in reflection configuration. The scanning results correctly match the distribution of delaminations inside the sample, which was proven with cross-sectional and frontal views after waterjet cutting. For further analysis, a signal-processing algorithm based on the deconvolution method was developed and the modified reference signal was used to reduce disturbances. The complex refractive index of the sample was determined by transmission TDS technique and was later used for the simulation of pulse propagation by the finite difference time domain method. These simulations verified the correctness of the proposed method and showed its constraints. Using the proposed algorithm, the ambiguous raw THz image was converted into a binary 3D image of the sample, which consists only of two areas: sample-polyethylene and delamination-air. As a r esult, a clear image of the distribution of delaminations with their spatial extent was obtained which can be used for further comparative analysis. The limitation of the proposed method is that parts of the central area of the puncture cannot be analyzed because tilted layers deflect the incident signal.