Microwave shielding and DC Electrical Properties of Carbon Black Loaded Rubber Nano-Composites

Abstract

In this work, ten carbon black (CB) loaded elastic acrylonitrile butadiene rubber (NBR) nano-composites have been prepared to be used in microwave shielding applications. The DC electric properties of these CB loaded NBR composites have been studied. The evolution of DC conductivity of CB loaded NBR composites with loading level revealed S-shapes curve in accordance with the percolation theory. The current (I)-voltage (V) relations have been studied for these samples at room temperature. All CB loaded NBR composite samples showed Ohmic behavior with the exception of two samples namely CB30 and CB40 in which space charge limited conduction is obvious. Microwave shielding has been calculated from the transmittance data measured using terahertz time domain spectroscopy (THz-TDS) technique. The analysis of microwave shielding data revealed that the sample CB70 has the highest shielding effectiveness. The results of the microwave shielding effectiveness of CB loaded NBR composites were correlated to their DC electric conductivities. Results showed that there is a strong relationship between the DC electric conductivity of the samples and their activity regarding microwave shielding effectiveness. The current investigation of microwave shielding properties of CB loaded NBR composites magnifies the importance of DC electric conduction losses as a major mechanism for microwave shielding.

http://www.jmest.org/wp-content/uploads/JMESTN42350842.pdf

TPS Spectra 3000, (TeraView, UK) was used for measuring transmittance of the samples in the frequency range 10-1000 GHz

ASSESSMENT METHODS FOR COMPOSITE AEROSPACE STRUCTURES

Summary:
In this paper result of detection and localization of artificially initiated delaminations in small carbon fibre reinforced polymer CFRP and glass fibre reinforced polymers GFRP samples were presented. The first method was electromechanical impedance method (EMI). This method utilizes electromechanical coupling of piezoelectric transducer with host structure. Due to this coupling mechanical resonances of structure can be seen in electrical impedance characteristic of piezoelectric transducer. Instead of electrical impedance other parameters such as resistance, conductance, admittance or susceptance are very often utilized. In the research real part of electrical impedance (resistance) was measured. Delamination in CFRP sample caused frequency shift of certain resonance frequencies visible in resistance characteristic. The second method was a laser vibrometry. It is a noncontact technique that allows to measure vibration of structure excited by piezoelectric transducer. During research standing waves (vibration–based method) and propagating waves (guided waves–based method) were registered for CFRP sample. In the vibration–based method, the frequency shifts of certain resonance frequencies were analyzed. In guided waves-based technique, the interaction of elastic waves with delamination can be seen in the RMS energy map. The third method is Terahertz spectroscopy. The device uses an electromagnetic radiation in the terahertz range (0.1–3 THz). The spectrometer is equipped with moving table that allows for XY scanning of large objects. During research the scanning heads working in reflection mode were utilized and the measurements were taken for GFRP sample with delamination. During research time signals as well as sets of signals creating B–scans and C–scans were analysed. The obtained results showed that the THz spectroscopy technique can detect and visualize delamination between the GFRP layers.

Teraview's TPS Spectra 3000 was used in these investigations

http://www.dem.ist.utl.pt/smart2015/files/SMART_2015_Proceedings/PDF/Papers/SMART2015_053.pdf

Advances in terahertz research - recent papers and publications

Technology Update: 

TeraView continues to support and promote fundamental and applied research within the terahertz field.

Each year the breadth and depth of interest in the area increases and TeraView is happy to help highlight these.

Below is a small selection of work from our customers and partners highlighting advances across a diverse range of application areas. These include work on; graphene, composite materials, explosives  and art conservation.

Chinese Academy of Sciences, Xi’an, China

Terahertz Spectral Investigation of Anhydrous and Monohydrated Glucose Using Terahertz Spectroscopy and Solid-State Theory

Woosuk University, Chonbuk, Republic of Korea

Influence of terahertz waves on the penetration in thick FRP composite materials

Chung-Ang University, Anseong, Republic of Korea

Foreign-body detection in dry food using continuous sub-terahertz wave imaging

University of Cambridge, Cambridge, United Kingdom

Low-Bias THz Amplitude Modulator Based on Split-Ring Resonators and Graphene

University College London, London, United Kingdom

Systematic study of terahertz time-domain spectra of historically informed black inks

Military University of Technology, Warsaw, Poland

Identification of concealed materials, including explosives, by terahertz reflection spectroscopy

To keep up to date with the latest articles and publications from TeraView, as well as gain access to an archive of all our publications, visit our website or our blog at:

Website: http://www.teraview.com/news/terahertz-publications/index.html

Influence of terahertz waves on the penetration in thick FRP composite materials

Kwang-Hee Im¹, David K. Hsu², Chien-Ping Chiou², Daniel J. Barnard², In-Young Yang³ and Je-Woong Park⁴


Abstract

Fiber reinforced plastics (FRP) are increasingly utilized in engineering structures because of their performance and fabrication advantages. With this increased utilization, a technique to gage quality and further characterize the materials would be beneficial. The nondestructive applications for Terahertz (T-ray) methods have also experienced increased utilization for evaluating engineering materials and will be reported on here in applications for the inspectionand characterization of FRP materials used in wind energy components. First, refraction and transmission T-ray modes are used to determine the refractive index (n) of a glass fiber reinforced plastic (GFRP) reference sample, and extended for calculating the refractive indicesfor a sample of GFRP, balsa and epoxy. Additionally, carbon fiber reinforced plastic (CFRP) samples were evaluated with respect to fiber directions versus T-ray electric field polarization direction to evaluate the level of penetration of T-ray energy due to the fiber orientation dependent conductivity of this composite material. Finally, an evaluation of T-ray data was made to evaluate resonance effects, where the resonance frequency was found to agree with that expected from reflections from individual plies in thick GFRP laminates.

This study was performed using TeraView's CW Spectra 400 system. (TeraView, Cambridge, UK)

Full Article: http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.4865010

Characterization of T-ray Penetration to Composite Materials

Kwang-Hee Im, David K. Hsu, Chien-Ping Chiou, Daniel J. Barnard and In-Young Yang

Department of Auto. Eng., Woosuk University 490, Samrae-up, Wanju-kun, Chonbuk, 565-701, Korea

Center for Nondestructive Evaluation, Iowa State University, Ames, Iowa 50011, USA

School of Mechanical Eng., Chosun University, 375 Seosuk-dong, Dong-gu, Kwangju 501-759, Korea

Abstract

Using T-ray (Terahertz waves) characterization of the non-destructive evaluation was made on the penetration on composite materials. The modalities of the T-ray radiation used were time domain spectroscopy (TDS) and continuous wave (CW) for composites. The composite materials investigated include both non-conducting polymeric composites and carbon fiber composites. T-ray signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, T-ray pulse can detect a crack hidden behind a larger crack (shadow effect). Thick GFRP laminates containing double saw cuts was tested. Also, in carbon composites the penetration of T-ray waves was investigated in order to detect flawsis strongly affected by the angle between the electric field vector of the terahertz waves and the intervening fiber directions. The T-ray effect was intensively studied between the carbon fiber direction and the electric field of T-ray. Other composites tested in this study include both solid laminates and honeycomb sandwiches. The defects and anomalies investigated by T-ray were foreign material inclusions, simulated disbond and delamination, mechanical impact damage, and water or hydraulic fluid ingression. The intensive characterization of T-ray for the NDE of composites is being discussed.

... 2. T-ray system 2.1 T-ray scanner The terahertz instrumentation systems used in this research
were provided by TeraView Limited. The instrumentation includes a time domain spectroscopy
(TDS) pulsed system and a frequency domain continuous wave (CW) system. ...

Keywords: T-ray, Time domain spectroscopy, Composite materials, Penetration.

Full paper

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