The Dielectric Constant of Air at Radiofrequencies

Hector, L. Grant; Schultz, H. L.

doi:10.1063/1.1745374

Cited by 66 publications

(34 citation statements)

References 4 publications

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“…As source function a time dependent surface charge located [39,40] at the hypothetical crack surface and the time dependent generation of the respective electric field is used. The electric potential V is calculated by solving a current conservation problem based on Ohm's law:…”

Section: Modellingmentioning

confidence: 99%

Relation of Electromagnetic Emission and Crack Dynamics in Epoxy Resin Materials

et al. 2014

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Electromagnetic emission (EME) testing and acoustic emission (AE) testing are applied to investigate the failure of a brittle, dielectric material under mechanical load. A setup for three point flexure tests comprising simultaneous monitoring of EME and AE was used to induce fracture of epoxy resin specimens. The influences of the orientation and the distance of the crack surface on the detectable EME signals are the subjects of investigation. As EME sensor a capacitive sensor was used. Tests with an artificial test source are carried out to characterize the system response of the sensor, the attached amplifier and acquisition cards as well as the included bandpass filters. We propose an EME source based on the surface charge density modelled at the position of the fracture plane. Results of finite element method modelling of the EME source are compared to experimental results and show very good agreement. The experimental results show a clear directional character of the emitted electromagnetic field and a strong dependence of the detected signals amplitude on sourcesensor distance. A significant influence of the measurement chain on the detected electromagnetic signals bandwidth was found. Furthermore it is shown that the electromagnetic signals consist of three contributions originating from different source mechanisms. These are attributed to the separation and

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Section: Modellingmentioning

confidence: 99%

Relation of Electromagnetic Emission and Crack Dynamics in Epoxy Resin Materials

et al. 2014

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“…This is validated by the phase angle plots which clearly show a shift in phase at fracture in the low frequency spectra. When the phase angle becomes zero, this implies that both the voltage and current are at the same phase and the material doesn't exhibit a capacitive nature, which was observed in normalized permittivity plots shown in Figure 10 [26]. When the same properties as neat resin were used, it was observed that there was no significant variation in the predicted dielectric response, and whatever variations were observed were due to changes in shape (geometry) as shown in Figure 11.…”

Section: Vadlamudi Et Almentioning

confidence: 63%

Multiphysics Based Simulation of Damage Progression in Composites

Vadlamudi¹,

Raihan²,

Reifsnider³

2017

MSA

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The long-term properties of continuous fiber reinforced composite materials are increasingly important as applications in airplanes, cars, and other safety critical structures are growing rapidly. Although a clear understanding has been established for initiation, growth and accumulation of damage, it is still unclear when and how the interactions of these local events lead to the development of a "critical" fracture path resulting in a sudden change of global properties and possible rupture. In the present paper, we simulate damage development in a neat polymeric resin using X-FEM analysis, and conduct concomitant dielectric response analysis with a COMSOL TM simulation model to study the collective defect structure as it develops in a model system. Our studies reveal inflection points in the predicted global dielectric response vs. strain that are related to changes in local damage growth rates and modes that clearly indicate impending fracture and capture the progressive change in material state.

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“…This measurement can then be looked on as an air reference calibration. According to the literature, the relative permittivity of air under normal condition is 1.00058986 ± 0.00000050 [14] and the loss factor is assumed to be small but dependent on humidity. However, for the present accuracy requirements, the relative permittivity of air can be set to unity with no losses.…”

Section: Air Reference Methodsmentioning

confidence: 99%

Enhanced accuracy in dielectric response material characterization by air reference method

Bengtsson

Blennow

et al. 2013

IEEE Trans. Dielect. Electr. Insul.

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This document has been downloaded from Chalmers Publication Library (CPL). It is the author´sversion of a work that was accepted for publication in: IEEE transactions on dielectrics and electrical insulation (ISSN: 1070-9878)Citation for the published paper: Xu, X. ; Bengtsson, T. ; Blennow, J. (2013) ABSTRACTDielectric response measurements are an important technique to characterize dielectric materials. However, the electrode arrangements as well as the accuracy of the measurement setup limit the precision of this characterization, especially in case of solid dielectric materials. An air reference method and a contact-free electrode arrangement are described in this paper to enhance the dielectric characterization accuracy by avoiding problems introduced by electrode contacts. It is shown that by performing a calibration with electrode gap filled with air under the same conditions as the material is tested, the air reference method can improve the measurement accuracy substantially. This type of approach also eliminates the need of a detailed model of the analog measurement circuit. In conjunction with the contact-free measurements, the approach allows for avoiding complicated and time-consuming sample preparation procedures. The measurement methodology as well as the electrode arrangement and error increase estimates are presented and evaluated by using different dielectric response instruments and materials.Index Terms -Dielectric material characterization, dielectric frequency response, air reference method, shunt characterization, contact-free electrode arrangement.

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The Dielectric Constant of Air at Radiofrequencies

Cited by 66 publications

References 4 publications

Relation of Electromagnetic Emission and Crack Dynamics in Epoxy Resin Materials

Relation of Electromagnetic Emission and Crack Dynamics in Epoxy Resin Materials

Multiphysics Based Simulation of Damage Progression in Composites

Enhanced accuracy in dielectric response material characterization by air reference method

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