Aeronautics composite material inspection with a terahertz time-domain spectroscopy system
16 Dec 2013-Optical Engineering (International Society for Optics and Photonics)-Vol. 53, Iss: 3, pp 031208-031208
TL;DR: In this paper, a mobile time-domain spectroscopy system that operates in reflection geometry was proposed for inspection of composite materials from the aeronautics industry, with the goal of developing a mobile mobile time domain spectroglobalization system.
Abstract: The usability of pulsed broadband terahertz radiation for the inspection of composite materials from the aeronautics industry is investigated, with the goal of developing a mobile time-domain spectroscopy system that operates in reflection geometry. A wide range of samples based on glass and carbon fiber reinforced plastics with various types of defects is examined using an imaging system; the results are evaluated both in time and frequency domain. The conductivity of carbon fibers prevents penetration of the respective samples but also allows analysis of coatings from the reflected THz pulses. Glass fiber composites are, in principle, transparent for THz radiation, but commonly with significant absorption for wavelengths >1 THz . Depending on depth, matrix material, and size, defects like foreign material inserts, delaminations, or moisture contamination can be visualized. If a defect is not too deep in the sample, its location can be correctly identified from the delay between partial reflections at the surface and the defect itself.
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TL;DR: The development of THz PCA technology through the last 30 years is reviewed, the key modalities of improving device performance are identified, and literature is reviewed to summarize the progress made in these areas.
Abstract: Photoconductive antennas (PCAs) have been extensively utilized for the generation and detection of both pulsed broadband and single frequency continuous wave terahertz (THz) band radiation. These devices form the basis of many THz imaging and spectroscopy systems, which have demonstrated promising applications in various industries and research fields. The development of THz PCA technology through the last 30 years is reviewed. The key modalities of improving device performance are identified, and literature is reviewed to summarize the progress made in these areas. The goal of this review is to provide a collection of all relevant literature to bring researchers up to date on the current state and remaining challenges of THz PCA technology.
264 citations
Cites background from "Aeronautics composite material insp..."
...Many works have studied the potential use of THz imaging and time-domain reflectometry as a quality control tool in electronics fabrication and packaging as well as composite material inspection.(21) Biomedical imaging using THz radiation has been proposed and studied for the purpose of cancer imaging, burn wound assessment, and dental tissue imaging....
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TL;DR: In this article, the authors review the recent advances in nondestructive testing and evaluation (NDT&E) as applied to the inspection of thick composite parts and sandwich structures and determine possible research prospects to address the limitations of current technologies.
126 citations
TL;DR: In this paper, the authors used reflective pulsed terahertz imaging to locate and size the forced delamination in polyetherimide resins in 3D dimensions and determined the thicknesses of the delamination and the layers constituting the laminate.
Abstract: Glass fiber-reinforced composite laminates in polyetherimide resin have been studied via terahertz imaging and ultrasonic C-scans. The forced delamination is created by inserting Teflon film between various layers inside the samples prior to consolidating the laminates. Using reflective pulsed terahertz imaging, we find high-resolution, low-artifact terahertz C-scan and B-scan images locating and sizing the delamination in three dimensions. Furthermore, terahertz imaging enables us to determine the thicknesses of the delamination and of the layers constituting the laminate. Ultrasonic C-scan images are also successfully obtained; however, in our samples with small thickness-to-wavelength ratio, detailed ultrasonic B-scan images providing quantitative information in depth cannot be obtained by 5 MHz or 10 MHz focused transducers. Comparative analysis between terahertz imaging and ultrasonic C-scans with regard to spatial resolution is carried out demonstrating that terahertz imaging provides higher spatial resolution for imaging, and can be regarded as an alternative or complementary modality to ultrasonic C-scans for this class of glass fiber-reinforced composites.
121 citations
TL;DR: In this article, the authors present different industrial applications, which have addressed with their terahertz systems within the last couple of years, and demonstrate thickness determination of multilayer plastic tube walls.
Abstract: Nondestructive quality inspection with terahertz waves has become an emerging technology, especially in the automotive and aviation industries. Depending on the specific application, different terahertz systems—either fully electronic or based on optical laser pulses—cover the terahertz frequency region from 0.1 THz up to nearly 10 THz and provide high-speed volume inspections on the one hand and high-resolution thickness determination on the other hand. In this paper, we present different industrial applications, which we have addressed with our terahertz systems within the last couple of years. First, we show three-dimensional imaging of glass fiber–reinforced composites and foam structures, and demonstrate thickness determination of multilayer plastic tube walls. Then, we present the characterization of known and unknown multilayer systems down to some microns and the possibility of measuring the thickness of wet paints. The challenges of system reliability in industrial environments, e.g., under the impact of vibrations, and effective solutions are discussed. This paper gives an overview of state-of-the-art terahertz technology for industrial quality inspection. The presented principles are not limited to the automotive and aviation industries but can also be adapted to many other industrial fields.
87 citations
TL;DR: In this paper, a terahertz (THz) pulsed spectroscopy (TPS) was used for non-destructive control of polymer binder polymerization, since THz radiation is sensitive to changes of picosecond dynamics in media.
Abstract: Nowadays, composite materials are widely used in building and construction industry, in motor-vehicles, spacecrafts and aircrafts, and in biomedical science due to the ability of combining various consistent components for manufacturing composite materials with physical and chemical properties significantly different from the properties of each component. Polymer composite materials (PCMs) appear to be the most common type of composites. PCMs consist mainly of polymer binder reinforced with the glass-fiber-fabric. Although PCMs are widely applied, PCM manufacturing technology lacks the methods of non- destructive testing. In this paper we demonstrate that terahertz (THz) pulsed spectroscopy (TPS) appears to be a unique instrument for solving important problems of PCM manufacturing control. We experimentally demonstrate the efficiency of TPS for non-destructive control of PCM binder polymerization, since THz radiation is sensitive to changes of picosecond dynamics in media. Furthermore, we show the ability to detect the internal non-impregnated voids inside the PCM structure by means of THz time-of-flight tomography. These results highlight the potentials of TPS applications for non-destructive control of PCM manufacturing process.
86 citations
References
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TL;DR: This work presents what is to their knowledge the first imaging system based on optoelectronic terahertz time-domain spectroscopy, and demonstrates applications to package inspection and chemical content mapping in biological objects.
Abstract: We present what is to our knowledge the first imaging system based on optoelectronic terahertz time-domain spectroscopy Terahertz time-domain waveforms are downconverted from the terahertz to the kilohertz frequency range, and the waveform for each pixel is frequency analyzed in real time with a digital signal processor to extract compositional information at that point We demonstrate applications to package inspection and chemical content mapping in biological objects
1,628 citations
TL;DR: A novel basic technology for terahertz imaging is developed, which allows detection and identification of drugs concealed in envelopes, by introducing the component spatial pattern analysis.
Abstract: The absence of non-destructive inspection techniques for illicit drugs hidden in mail envelopes has resulted in such drugs being smuggled across international borders freely. We have developed a novel basic technology for terahertz imaging, which allows detection and identification of drugs concealed in envelopes, by introducing the component spatial pattern analysis. The spatial distributions of the targets are obtained from terahertz multispectral transillumination images, using absorption spectra measured with a tunable terahertz-wave source. The samples we used were methamphetamine and MDMA, two of the most widely consumed illegal drugs in Japan, and aspirin as a reference.
1,309 citations
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TL;DR: In this paper, the authors describe the technology necessary to perform terahertz "T-ray" imaging, novel imaging techniques, and commercial applications of T-ray imaging.
Abstract: The use of terahertz pulses for imaging has opened new possibilities for scientific and industrial applications in the terahertz frequency range. In this article, we describe the technology necessary to perform terahertz "T-ray" imaging, novel imaging techniques, and commercial applications of T-ray imaging.
874 citations
TL;DR: Terahertz time domain spectroscopy was assessed as a nondestructive evaluation technique for aircraft composites and showed that burning did not change the refractive index or absorption coefficient noticeably, but material blistering was detected.
Abstract: Terahertz time domain spectroscopy (TDS) was assessed as a nondestructive evaluation technique for aircraft composites. Damage to glass fiber was studied 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 TDS transmissive imaging using amplitude and phase techniques. The depth of delaminations was measured via the timing of Fabry-Perot reflections after the main pulse. Evidence of bending stress damage and simulated hidden cracks was also detected with terahertz imaging.
323 citations
TL;DR: In this article, a combination of a Gunn diode emitter, a Schottky diode detector, and a polyethylene Fresnel lens was used for line-scan images at 0.2m∕s with a data acquisition rate of 512 points∕ s.
Abstract: We report the use of a compact continuous-wave sub-terahertz system for inspection applications, using electronic generation and detection methods. A combination of a Gunn diode emitter, a Schottky diode detector, and a polyethylene Fresnel lens provides line-scan images at 0.2m∕s with a data acquisition rate of 512points∕s. Examples of the measurement of NASA’s insulating panels and applicability of the technology to other nondestructive testing applications are presented and discussed.
307 citations