Terahertz Detection of Wavelength-Size Metal Particles in Pressboard Samples

Abstract

Results of a theoretical and experimental investigation of THz detection of randomly-oriented metal particles smaller than 1 mm embedded in pressboard are reported and critically compared with X-ray scanner results. A theoretical description based on Gaussian beam theory and a transfer function approach enabled simulation of signals transmitted around and reflected from real particles and was able to predict signal detectability. Simulated signals and detection limits were compared with experimental transmission and reflection time domain spectroscopy (TDS) raster scanning data. Simulated and measured pulse amplitude and shape were in agreement. Reflection mode was superior to transmission mode in terms of both particle visibility and hit ratio. Imaging of particles was also possible in “reflection in transmission” mode, which can be used to complement classical transmission mode. X-ray images did not detect the smallest particles sufficiently and, therefore, could not be used as reference data for comparison with THz data. The results demonstrate that TDS reflection scanning is able to determine the position of small metal particles and the technique could be possibly used for quality control of pressboard insulation.

Read full article here 

Terahertz Spectroscopy Applied For Investigation of Water Structure

Nikita Penkov, Nikolay Shvirst, Valery Alexandrovich Yashin, Eugeny Eugenievich Fesenko (Jr.), and Eugeny Eugenievich Fesenko

 Abstract

The absorption spectra of liquid water and different aqueous solutions were analyzed in a terahertz frequency domain (from 6 to 200 cm–1) which characterize the collective dynamics of water molecules. The particular attention was paid to the relaxation process in the range of ~6–80 cm-1. The physical essence of this process on the molecular level is still unclear. We found that the amplitude of this relaxation process correlates with the degree of destruction of water structure. The obtained data allowed us to interpret this process as a monomolecular relaxation of free water molecules. Based on a consideration of the water polarization in the electric field we proposed a method of calculation of the amount of free water molecules in solution.

If you would like to read more please use this link.

Microelectromechanically tunable multiband metamaterial with preserved isotropy

Abstract

We experimentally demonstrate a micromachined reconfigurable metamaterial with polarization independent characteristics for multiple resonances in terahertz spectral region. The metamaterial unit cell consists of eight out-of-plane deformable microcantilevers placed at each corner of an octagon ring. The octagon shaped unit cell geometry provides the desired rotational symmetry, while the out-of-plane movable cantilevers preserves the symmetry at different configurations of the metamaterial. The metamaterial is shown to provide polarization independent response for both electrical inductive-capacitive (eLC) resonance and dipolar resonance at all states of actuation. The proposed metamaterial has a switching range of 0.16 THz and 0.37 THz and a transmission intensity change of more than 0.2 and 0.7 for the eLC and dipolar resonances, respectively for both TE and TM modes. Further optimization of the metal layer thickness, provides an improvement of up to 80% modulation at 0.57 THz. The simultaneously tunable dual band isotropic metamaterial will enable the realization of high performance electro-optic devices that would facilitate numerous terahertz applications such as compressive terahertz imaging, miniaturized terahertz spectroscopy and next generation high speed wireless communication possible in the near future.

All THz transmission spectra measured in this paper were acquired using TeraView's TPS Spectra 3000.

http://www.nature.com/srep/2015/150626/srep11678/full/srep11678.html

TeraView TPS 3000 unit for time domain spectroscopy was used to investigate spectral properties of nematic liquid crystal mixtures

Article

Spectral Properties of Nematic Liquid Crystal Mixtures Composed with Long and Short Molecules in THz Frequency Range

ABSTRACT In this paper the influence of short and long molecules added to liquid crystal
6CHBT were investigated. Change of refractive indices and absorption coefficients
for 6CHBT mixtures were compared in the 0.3 - 3 THz frequency range. Influence of
temperature on the mentioned parameters of liquid crystal were investigated. Our study
show that even a slight change in shape and the composition of the molecules dopants
affects the macroscopic properties of liquid crystal. These properties depend on the
length of chains, the number of benzene or cyclohexane rings or the spatial distribution
of molecules and the interactions between them in the liquid crystal mixture. Spectra
measurements on the terahertz time-domain spectrometer were performed.
Spectral Properties of Nematic Liquid Crystal Mixtures Composed with Long and Short Molecules in THz Frequency Range (PDF Download Available). Available from: http://www.researchgate.net/publication/235218799_Spectral_Properties_of_Nematic_Liquid_Crystal_Mixtures_Composed_with_Long_and_Short_Molecules_in_THz_Frequency_Range [accessed Jun 23, 2015].

IRMMW-THz 2013

Mainz on the Rhine, September 1st-6th

TeraView will be attending IRMMW-THz 2013.

The 38th Annual International Conference on Infrared, Millimeter, and Terahertz Waves will be held in Mainz, Germany, on September 1 - 6, 2013, at the Congress Center Mainz (Rheingoldhalle). The conference is organized by a Local Organizing Committee under the auspices of the IOC, and with technical co-sponsorship from the IEEE Microwave Theory and Techniques Society (MTT-S).

Dr. Phil Taday will be presenting a paper with title: 

Crystallization Of Sucrose Monitored By Terahertz Pulsed Spectroscopy
Session: Mo. 9 - THz Spectroscopy: Biomolecules
Abstract ID: Mo9-1
Date: 02/09/2013
Time: 2:00:00 PM

If you would like to pre-arrange a meeting, please e-mail Dr. Philip Taday. For more information and to attend the workshop please visit the event webpage.

To view all conferences that TeraView will be attending please visit our website

TeraView will also be exhibiting at this conference.

Terahertz Time Domain Spectroscopy of Human Blood

Biomedical and Health Informatics, IEEE Journal of
Issue: 99
Authors: Reid, C; Reese, G.; Gibson, A.P.; Wallace, V.P.
Department of Medical Physics and Bioengineering, University College London

Abstract

In the continuing development of terahertz technology to enable the determination of tissue pathologies in real-time during surgical procedures, it is important to distinguish the measured terahertz signal from biomaterials and fluids, such as blood, which may mask the signal from tissues of interest. In this paper, we present the frequency-dependent absorption coefficients, refractive indices and Debye relaxation times of whole blood, red blood cells, plasma and a thrombus.

... Methods Experimental method A stand-alone portable THz system, the TPI Imaga1000 (TeraView Ltd, Cambridge, UK), was used in this work. A full description of the system operation is given elsewhere [19], however it is briefly described here for clarity...

More info at: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6506093&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6506093

THz periodic surfaces to enhance spectroscopic measurements

Proceeding from the International Conference on Electromagnetics in Advanced Applications (ICEAA), 2012 | 2-7 Sept. 2012

Authors: Woon-Gi Yeo¹, Sanphuang, V.²; Nahar, N.K.1; Volakis, J.L.³

1. Dept. of Electr. & Comput. Eng., +The Ohio State University, Columbus, OH, USA
2. Fac. of Eng. & Technol., Asian Univ., Chon Buri, Thailand 
3. Radiat. Lab., Michigan Univ., Ann Arbor, MI, USA 

Abstract 

We present a multi-layered frequency selective surfaces (FSS) exhibiting low losses for broad band spectroscopic measurements in THz frequencies. The intent is to replace existing samples holders (e. g. z-cut crystal quartz) with transparent metamaterial layers and increase measurement sensitivity. To enable multiband and broadband responses, a multilayered FSS is proposed, and thus suppress losses in a given range of THz bands.

More details at: http://dx.doi.org/10.1109/ICEAA.2012.6328766

Investigation on the Terahertz Absorption Spectra of the Molecules with Similar Molecular Structure

Conference Paper from Laser and Tera-Hertz Science and Technology

Wuhan, China, November 1, 2012
THz Spectroscopy and Imaging (SF3A)
Author: Wenhui Fan; http://dx.doi.org/10.1364/LTST.2012.SF3A.1
+The Optical Society (OSA)

Abstract

The characteristic terahertz absorption features of several molecules with similar molecular structure have been measured by terahertz time-domain spectroscopy experimentally. Theoretical simulations have also been performed, and all measured terahertz absorption features are assigned.

More info at: http://www.opticsinfobase.org/abstract.cfm?URI=LTST-2012-SF3A.1

Using Terahertz Spectroscopy for Observing the Kinetics of Recrystallisation of Polybutene-1

Journal of Infrared, Millimeter, and Terahertz Waves

February 2013, Volume 34, Issue 2, pp 187-193
doi: 10.1007/s10762-013-9956-8

Authors: V. Křesálek, T. Gavenda
More details at: http://link.springer.com/article/10.1007/s10762-013-9956-8

Abstract

This paper deals with the use of terahertz spectroscopy for observing the kinetics of recrystallisation of polybutene-1 as a suitable material for manufacturing optical elements in the terahertz region of the electromagnetic spectrum. These materials were studied from the perspective of their optical properties – the refractive index and the absorption coefficient. The time dependencies of the refractive index and the absorption coefficient were measured, because polybutene-1 is a material which recrystallises for a number of days from the date of its manufacture. The coefficients describing the recrystallisation process were calculated from the fitting function derived from the Avrami equation. In this paper, the measurement results are presented and the possibilities of the use of the studied materials are discussed.

...Measurement was conducted by a TPS^TM Spectra 3000...Thickness was measured at 12 points of each sample to achieve the desired accuracy, after averaging the measured values. The calculation of the refractive index and absorption coefficient was performed with the TPS^TM Spectra 3000 software, with air as the reference value...

Terahertz Spectroscopy and Imaging - New Book

Series: Springer Series in Optical Sciences, Vol. 171,2013, XXXI, 641 p.

Authors: Peiponen, Kai-Erik; Zeitler, Axel; Kuwata-Gonokami, Makoto (Eds.

+SpringerMaterials
More details at: http://www.springer.com/physics/optics+%26+lasers/book/978-3-642-29563-8

• Presents the state-of-the-art of Terahertz spectroscopy
• Gives a concise presentation of the basics of THz spectroscopy
• Describes important applications of THz technology

"This book presents the current state of knowledge in the field of terahertz spectroscopy, providing a comprehensive source of information for beginners and experienced researchers alike whose interests lie in this area. The book aims to explain the fundamental physics that underpins terahertz technology and to describe its key applications. Highlights of scientific research in the field of terahertz science are also outlined in some chapters, providing an overview as well as giving an insight into future directions for research.

Over the past decade terahertz spectroscopy has developed into one of the most rapidly growing areas of its kind, gaining an important impact across a wide range of scientific disciplines. Due to substantial advances in femtosecond laser technology, terahertz time-domain spectroscopy (THz-TDS) has established itself as the dominant spectroscopic technique for experimental scientists interested in measurements at this frequency range. In solids and liquids THz radiation is in resonance with both phonon modes and hydrogen bonding modes, which makes it an ideal tool to study the interaction between molecules in a unique way; thus opening a wealth of opportunities for research in physics, chemistry, biology, materials science and pharmaceuticals.

This book provides easy access to scientists, engineers and students who want to understand the theory and applications of modern THz spectroscopy."

Chapter: Industrial Applications of Terahertz Imaging

This chapter gives a concise overview of potential industrial applications for terahertz imaging that have been reported over the past decade with a discussion of the major advantages and limitations of each approach. In the second half of the chapter we discuss in more detail how terahertz imaging can be used to investigate the microstructure of pharmaceutical dosage forms. A particular focus in this context is the nondestructive measurement of the coating thickness of polymer coated tablets, both by means of high resolution offline imaging in research and development as well as for in-line quality control during production.


... Defect in copper trace (a) (b) Fig. 18.3 Electro Optical Terahertz Pulse Reflectometry (EOTPR) for semiconductor fault testing. a Optical images of the two failed devices showing the cut in the copper traces. b Results obtained with EOTPR (source: TeraView Ltd.) ...

More on applications of terahertz technology http://www.teraview.com/applications/index.html

Terahertz Conductivity of Twisted Bilayer Graphene

Physical Review Letters 110, 067401 (2013)  Received 9 April 2012; published 7 February 2013
doi:10.1103/PhysRevLett.110.067401

Authors: Xingquan Zou1, Jingzhi Shang¹, Jianing Leaw¹, Zhiqiang Luo¹, Liyan Luo¹, Chan La-o-vorakiat¹, Liang Cheng¹, S. A. Cheong¹, Haibin Su², Jian-Xin Zhu³, Yanpeng Liu⁴, Kian Ping Loh⁴, A. H. Castro Neto⁵, Ting Yu¹, and Elbert E. M. Chia¹

1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
2. Division of Materials Science, School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore
3. Theoretical Division and Center for Integrated Nanotechnologies, +Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
4. Department of Chemistry, +National University of Singapore , 3 Science Drive 3, 117543 Singapore
5. Graphene Research Centre and Physics Department, National University of Singapore, 6 Science Drive 2, 117546 Singapore

More details at: http://prl.aps.org/abstract/PRL/v110/i6/e067401

Abstract

Using terahertz time-domain spectroscopy, the real part of optical conductivity [σ1(ω)] of twisted bilayer graphene was obtained at different temperatures (10–300 K) in the frequency range 0.3–3 THz. On top of a Drude-like response, we see a strong peak in σ1(ω) at ∼2.7  THz. We analyze the overall Drude-like response using a disorder-dependent (unitary scattering) model, then attribute the peak at 2.7 THz to an enhanced density of states at that energy, which is caused by the presence of a van Hove singularity arising from a commensurate twisting of the two graphene layers.
© 2013 +American Physical Society

... The transmission THz spectra of the BLG were measured using a conventional THz-TDS system (TeraView TPS Spectra 3000)... THz TDS has proven to be a very useful noncontact technique to study material properties such as dielectric response, complex conductivity and refractive index in the far-infrared range without the need for Kramers-Kronig analysis ...

Towards optoelectronic detection of explosives

Opto-Electronics Review, June 2013, Volume 21, Issue 2, pp 210-219

doi 10.2478/s11772-013-0082-x

Authors: J. Wojtas, T. Stacewicz, Z. Bielecki, B. Rutecka, R. Medrzycki, J. Mikolajczyk
More details at: http://link.springer.com/article/10.2478/s11772-013-0082-x

Abstract

Detection of explosives is an important challenge for contemporary science and technology of security systems. We present an application of NOx sensors equipped with concentrator in searching of explosives. The sensors using CRDS with blue — violet diode lasers (410 nm) as well as with QCL lasers (5.26 μm and 4.53 μm) are described. The detection method is based either on reaction of the sensors to the nitrogen oxides emitted by explosives or to NOx produced during thermal decomposition of explosive vapours. For TNT, PETN, RDX, and HMX the detection limit better than 1 ng has been achieved.

... Time domain spectroscopy (TDS) is especially useful in the THz range [12,13]. Observation of explosives' transmission and reflection are conducted by using TeraView TPS Spectra 3000 instrument at the Institute of Optoelectronics, MUT ...

Author Affiliations: Institute of Optoelectronics, Military University of Technology, 2 Kaliskiego Str., 00-908, Warsaw, Poland

In 2011 TeraView supplied two TPS Spectra 3000 systems with a stand-off explosives detection module and a fibre-fed scanning system with multiple gantry options for research into terahertz imaging and non-destructive testing. Military University of Technology (MUT) in Poland is one of the country’s most prestigious research institutes for terahertz research and materials characterisation. Read more...

Crystal engineering approach to produce complex of azelnidipine with maleic acid

Authors: Weiguang Lian ,  Dong Li ,  Min Wang ,  Caiqin Yang and Jing Wang
+RSC,CrystEngComm, 2013, Accepted Manuscript
DOI: 10.1039/C3CE26967A
Received 05 Dec 2012, Accepted 09 Mar 2013
First published on the web 12 Mar 2013

...THz spectra were acquired on TeraView's TPI spectra 1000 transmission spectrometer...

Abstract

A novel azelnidipine-maleic acid complex was prepared by the solvent-assisted cogrinding method. The obtained complex was characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), infrared (IR), Raman, solid-state nuclear magnetic resonance (ssNMR), and terahertz (THz) spectroscopy. The PXRD and DSC measurement identified new different crystal form of the obtained complex other than those of the single azelnidipine and maleic acid. It was revealed that the azelnidipine-maleic acid complex was formed at a molar ratio of 2:1. IR, Raman and ssNMR spectroscopy verified that C-H...O hydrogen bond was formed between C=O from maleic acid and methyl group from azelnidipine. The distinctive THz spectrum showed that the vibrational mode of the complex was different from those of the starting materials, suggesting that THz spectroscopy is an ideal tool to evaluate complex formation. The solubilities of azelnidipine in maleic acid with different concentrations at different temperatures were investigated; the obtained values were used to calculate the formation constants and thermodynamic parameters. The improved dissolution rate in vitro of the complex showed potential to improve the physicochemical properties of azelnidipine API by crystal engineering approach.


More info at: http://pubs.rsc.org/en/content/articlelanding/2013/ce/c3ce26967a

Spectral Properties of Nematic Liquid Crystal Mixtures Composed with Long and Short Molecules in THz Frequency Range

Molecular Crystals and Liquid Crystals

Volume 561, Issue 1, 2012

Special Issue: Proceedings of the 14th International Topical Meeting: Optics of Liquid Crystals (OLC 2011): Part III of III

U. Chodorow, J. Parka, K. Garbat, N. Pałka, K. Czupryński and L. Jaroszewicz

Institute of Applied Physics, Military University of Technology, Warsaw, Poland

Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Warsaw, Poland

Institute of Chemistry, Military University of Technology, Warsaw, Poland

Institute of Optoelectronics, Military University of Technology, Warsaw, Poland

Abstract

Properties of liquid crystal materials in THz frequency range can be interesting from application point of view.

In this paper the influence of short and long molecules added to liquid crystal 6CHBT were investigated. Change of refractive indices and absorption coefficients for 6CHBT mixtures were compared in the 0.3 - 3 THz frequency range. Influence of temperature on the mentioned parameters of liquid crystal were investigated. Our study show that even a slight change in shape and the composition of the molecules dopants affects the macroscopic properties of liquid crystal. These properties depend on the length of chains, the number of benzene or cyclohexane rings or the spatial distribution of molecules and the interactions between them in the liquid crystal mixture. Spectra measurements on the terahertz time-domain spectrometer were performed.

................Teraview TPS 3000 unit with accessories in transmission configuration for Time Domain Spectroscopy measurement.............

For more information about the TPS spectra 3000 register for free here  or (http://www.teraview.com/info/)

Characterisation of historic plastics using terahertz time-domain spectroscopy and pulsed imaging

ANALYTICAL AND BIOANALYTICAL CHEMISTRY

DOI: 10.1007/s00216-012-5931-9

Gianluca Pastorelli, Tanja Trafela, Phillip F. Taday, Alessia Portieri, David Lowe, Kaori Fukunaga and Matija Strlič

For more information see http://www.springerlink.com/content/218682g6809873l1/


Abstract
Terahertz (THz) time-domain spectroscopy and 3D THz pulsed imaging have been explored with regard to polymer materials, both commodity and historic polymers. A systematic spectroscopic study of a wide range of different polymer materials showed significant differences in their spectra. Polyolefins and polystyrenes generally exhibit lower absorption than other examined polymers, various cellulose derivates, poly(vinyl chloride), poly(methyl methacrylate), polyamide, hard rubber and phenol formaldehyde resin, the last of these exhibiting the most intense absorption over the entire range, 0.15–4.2 THz. It was also examined how the presence of plasticisers in poly(vinyl chloride), the presence of fillers in polypropylene, and the degree of branching in polyethylene and polystyrene affect the spectra; inorganic fillers in polypropylene affected the absorption most. With 3D THz pulsed imaging, features in polymer objects were explored, appearing either as integral parts of the material (coatings and pores in foams) or as a consequence of physical deterioration (cracks, delamination). All of these features of various complexities can be successfully imaged in 3D. Terahertz technology is thus shown to have significant potential for both chemical and structural characterisation of polymers, which will be of interest to heritage science, but also to the polymer industry and development of analytical technologies in general.


For more information on terahertz imaging visit http://www.teraview.com/products/terahertz-pulsed-spectra-3000/index.html

Dielectric Properties of Monoclonal Antibodies to Influenza Using Terahertz Spectroscopy

From the Proceedings of 2011 International Conference on Opto-Electronics Engineering and Information Science (ICOEIS 2011)


Abstract. In this paper we use terahertz spectroscopy to study the effects of the monoclonal antibody to influenza A and the monoclonal antibody to influenza B. The complex permittivity was measured over the frequency range 0.1-1.7 THz.
The investigated antibodies can be distinguished by the frequency dependence of the dielectric properties. Therefore terahertz spectroscopy may be useful for medical diagnoses where the presence of antibodies is indicative of disease.


...TPI Imaga 1000 (TeraView Limited, Cambridge, UK) was used to determine the
terahertz 1535 Page 2. dielectric response...


http://www.asaas.org/ICOEIS2011/N361.pdf

Maskless multiple-beam laser lithography for large-area nanostructure/microstructure fabrication

Min Tang, Zai Chun Chen, Zhi Qiang Huang, Yoo Sang Choo, andMing Hui Hong

Applied Optics, Vol. 50, Issue 35, pp. 6536-6542 (2011)
http://dx.doi.org/10.1364/AO.50.006536

Abstract

This paper reports a maskless multiple-beam laser lithography technique for large-area nanostructure/microstructure fabrication. This lithography technique can flexibly generate arbitrary nanostructures/microstructures over a large area at a high speed. The feature size of the nanostructures/microstructures can be controlled by exposure time and moving speed of the nanostage. Functional predesigned patterns, including split-ring resonator metamaterials for terahertz waves, can be obtained. More complicated structures can be made by single- and double-exposure schemes to make hybrid nanostructures/microstructures and tune surface plasmonic resonance properties. Meanwhile, microstructures with large height to lateral dimension ratios (2.5D microstructures) fabricated on silicon substrates can be used as mold tools for soft lithography. This technology shows its unique capacity to create various nanostructures/microstructures for extensive applications.

Measurements were performed using TeraView's TPS Spectra 3000 

... The line width of the SRR structure is ∼6μm, and the SRR dimension is 40μm. The trans-
mission spectra of the terahertz metamaterials are characterized by a terahertz time-domain
spectro- scope (TeraView, TPS3000) with a normal incident ...

Citation
Min Tang, Zai Chun Chen, Zhi Qiang Huang, Yoo Sang Choo, and Ming Hui Hong, "Maskless multiple-beam laser lithography for large-area nanostructure/microstructure fabrication," Appl. Opt. 50, 6536-6542 (2011)
http://www.opticsinfobase.org/abstract.cfm?URI=ao-50-35-6536

View Full Text: Acrobat PDF (747 KB)

Collective Mode Frequency Shifts in L-Serine and a Series of Isotopologues in the Terahertz Regime

by: David C. Hufnagle, Anita R. Taulbee-Combs, Wolfgang U. Spendel, Gilbert E. Pacey


Abstract

Terahertz (THz) time-domain spectroscopy was used to monitor collective mode shifts in L-serine, L-serine-2,3,3-d3, L-serine-d4, and L-serine-d7 at both room and liquid nitrogen (LN2) temperatures. Increasing the molecular mass by deuteration caused an expected absorbance red-shift; however, the magnitude of the displacement could not be predicted using normal mode analysis. Both modes at 67.8 cm−1 and 91.4 cm−1 demonstrated a greater peak shift upon deuterium substitution at non-hydrogen bonding sites than at sites that participated in hydrogen bonding. This is evident in the larger peak shifts observed in L-serine-d3 than in L-serine-d4, despite a smaller increase in mass. This leads to the conclusion that both peaks present in the room temperature spectra of L-serine likely arise primarily from other intermolecular interactions with <50% contribution from hydrogen bonding. This goes against the prediction that peaks in the THz spectra of amino acids are predominantly due to the hydrogen bonding network that makes up the crystal lattice.

View Abstract

AIP Conf. Proc. / Volume 1335 / Issue 1

AN EXPLORATION OF THE UTILITIES OF TERAHERTZ WAVES FOR THE NDE OF COMPOSITES

AIP Conf. Proc. -- June 23, 2011 -- Volume 1335, pp. 533-540
REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Volume 30A; Volume 30B; doi:10.1063/1.3591897

ABSTRACT

Issue Date: 23 June 2011

David K. Hsu, Kwang-Hee Im, Chien-Ping Chiou, and Daniel J. Barnard
Center for Nondestructive Evaluation, Iowa State University, Ames, Iowa 50011


We report an investigation of terahertz waves for the nondestructive evaluation of composite materials and structures. The modalities of the terahertz radiation used were time domain spectroscopy (TDS) and continuous wave (CW). The composite materials and structures investigated include both non-conducting polymeric composites and carbon fiber composites. Terahertz signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, a terahertz pulse can detect a crack hidden behind a larger crack. This was demonstrated in thick GFRP laminates containing double saw slots. In carbon composites the penetration of terahertz waves is quite limited and the detection of flaws is strongly affected by the angle between the electric field vector of the terahertz waves and the intervening fiber directions. The structures tested in this study include both solid laminates and honeycomb sandwiches. The defects and anomalies investigated by terahertz waves were foreign material inclusions, simulated disbond and delamination, mechanical impact damage, heat damage, and water or hydraulic fluid ingression. The effectiveness and limitations of terahertz radiation for the NDE of composites are discussed. ©2011 American Institute of Physics


View abstract online