Non-destructive testing of glass fibre reinforced plastics with a synthetic aperture radar in the lower THz region

Nezadal, Martin; Schür, Jan; Schmidt, Lorenz-Peter

doi:10.1109/irmmw-thz.2012.6380301

Cited by 19 publications

(10 citation statements)

References 2 publications

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“…It was showed that the terahertz time-domain spectroscopy technology could be used to detect structural information and vibration of molecules, and applied to identify fibers [19]. Nezadal et al [20] used a low terahertz frequency band (frequency range of 220-325 GHz) to detect manmade defects in fiberglass reinforced plastics, which can reach a longitudinal resolution of 0.8 mm.…”

Section: Introductionmentioning

confidence: 99%

Novel Terahertz Spectroscopy Technology for Crystallinity and Crystal Structure Analysis of Cellulose

et al. 2020

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Crystallinity is an essential indicator for evaluating the quality of fiber materials. Terahertz spectroscopy technology has excellent penetrability, no harmful substances, and commendable detection capability of absorption characteristics. The terahertz spectroscopy technology has great application potential in the field of fiber material research, especially for the characterization of the crystallinity of cellulose. In this work, the absorption peak of wood cellulose, microcrystalline cellulose, wood nano cellulose, and cotton nano cellulose were probed in the terahertz band to calculate the crystallinity, and the result compared with XRD and FT-IR analysis. The vibration model of cellulose molecular motion was obtained by density functional theory. The results showed that the average length of wood cellulose (WC) single fiber was 300 μm. The microcrystalline cellulose (MCC) was bar-like, and the average length was 20 μm. The cotton cellulose nanofiber (C-CNF) was a single fibrous substance with a length of 50 μm, while the wood cellulose nanofiber (W-CNF) was with a length of 250 μm. The crystallinity of cellulose samples in THz was calculated as follows: 73% for WC, 78% for MCC, 85% for W-CNF, and 90% for C-CNF. The crystallinity values were obtained by the three methods which were different to some extent. The absorption peak of the terahertz spectra was most obvious when the samples thickness was 1 mm and mixed mass ratio of the polyethylene and cellulose was 1:1. The degree of crystallinity was proportional to the terahertz absorption coefficients of cellulose, the five-movement models of cellulose molecules corresponded to the five absorption peak positions of cellulose.

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Section: Introductionmentioning

confidence: 99%

Novel Terahertz Spectroscopy Technology for Crystallinity and Crystal Structure Analysis of Cellulose

et al. 2020

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“…It will be positive and negative for upward and downward shifts respectively. Based on the Δ ≤ /4, where = and the amplitude constraint on can be calculated by solving the following inequality As of quadratic polynomial, two roots of , and will be generated by (9), the minimum root defines the amplitude constraint on…”

Section: B Analysis Of Different Localization Cut-off Requirement Inmentioning

confidence: 99%

“…Nowadays, the THz SAR testbeds are being actively proposed in the literature and the research is being carried out for different potential applications such as defense [6][7], automobile [8], non-destructive testing [9], space-debris observation [10], and road mapping [11]. In this paper, an unmanned aerial vehicle (UAV) based THz SAR for an indoor environment is proposed that can be utilized for room mapping and material characterization.…”

Section: Introduction and Related Workmentioning

confidence: 99%

Indoor THz SAR Trajectory Deviations Effects and Compensation With Passive Sub-mm Localization System

et al. 2020

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In radar remote sensing, the Terahertz (THz) spectrum is presently being investigated worldwide with focus on short-range indoor and outdoor applications. The spectrum broadens the unmanned aerial vehicle (UAV) based synthetic aperture radar (SAR) applications to indoor room profiling with submm resolution and material characterization as many materials have unique fingerprints at this spectrum. SAR technique requires precise localization information of the mobile radar sensor, which in conventional SAR is achieved using an existing localization infrastructure, such as a global positioning system (GPS) and inertial measurement unit (IMU). For the indoor THz SAR, the GPS does not provide coverage in indoor complex environments, and also the state-of-art compact IMU does not provide the required sub-mm accuracy. These limitations can be overcome by utilizing an indoor localization system. Therefore, this paper presents an indoor THz simultaneous localization and mapping (SLAM) system. The system comprises of passive tags based radio frequency identification (RFID) localization system and SAR that provides the UAV localization and mapping of the in-room objects. Another challenge for the UAV based indoor THz SAR that is addressed in this paper is motion compensation (MOCO). At the THz, MOCO requires special consideration due to very small trajectory deviation is in the range of carrier wavelength. Therefore, to study the effects of the sub-mm translational errors, a testbed has been set up, and measurement results are presented in this paper along with the 3D electromagnetic simulation results for a carrier frequency of 275 GHz and bandwidth of 50 GHz. Further, to compensate these errors, the sub-mm localization system is used and the results are presented to validate the proposed solution for indoor THz SAR MOCO.

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“…In der THz-Technik werden diese Probleme durch die Verwendung vergleichsweise hoher Prüffrequenzen umgangen. Bei dieser Technik treten Beugungsmuster von Ecken und Kanten im Vergleich zu niedrigen Frequenzen nur in abgeschwächter Form auf, dafür ist sie aufgrund des erhöhten technischen Aufwands allerdings auch immer noch recht teuer und die Eindringtiefe der hochfrequenten Mikrowellen in das Material ist aufgrund der starken Dämpfung begrenzt [10][11][12][13]…”

Section: Introductionunclassified

P1.18 Objektrekonstruktion in der Mikrowellen-Defektoskopie

Gagelmann¹,

Nesterov²,

Wöckel³

et al. 2019

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Non-destructive testing of glass fibre reinforced plastics with a synthetic aperture radar in the lower THz region

Cited by 19 publications

References 2 publications

Novel Terahertz Spectroscopy Technology for Crystallinity and Crystal Structure Analysis of Cellulose

Novel Terahertz Spectroscopy Technology for Crystallinity and Crystal Structure Analysis of Cellulose

Indoor THz SAR Trajectory Deviations Effects and Compensation With Passive Sub-mm Localization System

P1.18 Objektrekonstruktion in der Mikrowellen-Defektoskopie

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