Bounds on the complex permittivity of a two‐component composite material

1981 ◽  
Vol 52 (8) ◽  
pp. 5286-5293 ◽  
Author(s):  
G. W. Milton
Keyword(s):  
Composite Material ◽  
Complex Permittivity ◽  
Two Component

The Study of Dielectric Constant Inversion of Coconut Fiber/Gypsum Composite Based on the λ/4 Absorption Spectrum

2014 ◽  
Vol 1030-1032 ◽  
pp. 400-403
Author(s):  
Qian Qian Chu ◽  
Hui Chao Zhao ◽  
Wan Jun Hao ◽  
Ying Ying Yi ◽  
Yi Feng Dong ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Composite Material ◽  
Absorption Spectrum ◽  
Composite Materials ◽  
Experimental Verification ◽  
Complex Permittivity ◽  
Functional Materials ◽  
Coconut Fiber ◽  
Inversion Theory ◽  
Equivalent Complex

The measurement of the complex permittivity of big structure composite material has always been a key and difficulty in the preparation of electromagnetic functional materials. In this paper the average dielectric constant inversion of coconut fiber/gypsum composite in S band is studied based on λ/4 absorption spectrum. First the absorbing effects of the prepared coconut fiber gypsum composite materials are tested with method of flat reflection. Then the equivalent complex permittivity is inversed with the inversion theory. Further the experimental verification is preceded that the theoretical and experimental absorbing curves whose peak positions are respectively at 3.05GHz and 2.45GHz are quite matched. And the study shows that this method is scientific and effective, and it can provide technical support for the baroque electromagnetic functional composite materials.

Improved bounds on the conductivity of composites by interpolation

1994 ◽  
Vol 444 (1921) ◽  
pp. 363-374 ◽  
Keyword(s):  
Composite Material ◽  
Lower Bounds ◽  
Approximation Method ◽  
Interpolation Method ◽  
Padé Approximation ◽  
Upper Bounds ◽  
Pade Approximation ◽  
Two Component ◽  
Null Lagrangian

Different bounds on the conductivity of a composite material may improve on each other in different conductivity régimes. If so, the question arises of how to efficiently interpolate between the bounds. In this paper I show how to do an interpolation with a two-point Padé approximation method. For bounds on two-component composites the interpolation method is shown to be, in a sense, the best possible. The method is discussed in the context of equiaxed polycrystals where the classic Hashin-Shtrikman bounds and the more recent null-lagrangian bounds, partly improve on each other. Denoting the principal conductivities of the crystallite σ 1 ≼ σ 2 ≼ σ 3 , the method gives improved lower bounds for equiaxed polycrystals which have σ 2 (0.77σ 1 + 0.23σ 3 ) ≽ σ 1 σ 3 . The method also gives improved upper bounds.

Effect of Heat Treatment on Microstructures and Hardness of SiC/Steel Armor Composite

2012 ◽  
Vol 724 ◽  
pp. 431-434
Author(s):  
Jie Dong ◽  
Jie Pan ◽  
Miao Wang ◽  
Cong Rong Zhang ◽  
Wei Liu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Composite Material ◽  
Iron Silicide ◽  
Heat Treatments ◽  
Isothermal Quenching ◽  
Treatment Situation ◽  
Two Component ◽  
The Matrix

The SiC reinforced ferrous based armor composites were treated with three heat treatments of annealing, isothermal quenching and annealing. The relationships between the treatment processing and the microstructures and hardness of the composite material were investigated. The results revealed that the heat treatment had scarcely any influence on the reinforced component but there appeared iron silicide existing at the interface of the two component, and the hardness of the component changed in three same treatment situation, the highest hardness of the matrix reached 532HB after subjecting to the isothermal quenching at 300°C.

Analysis of Absorption Properties for Magnetism-Absorbing Agents Mixed with Semiconductor Particulate

2012 ◽  
Vol 512-515 ◽  
pp. 1128-1131
Author(s):  
Chao Wu ◽  
Zhao Yang Zeng ◽  
Xu Liang Lü ◽  
Q. Jia ◽  
H.C. Tang
Keyword(s):  
Composite Material ◽  
Electromagnetic Wave ◽  
Attenuation Coefficient ◽  
Complex Permittivity ◽  
Impedance Matching ◽  
Absorption Properties ◽  
Mixed Ferrite ◽  
Microwave Absorbing ◽  
Real Complex

In order to improve absorbing properties of material effectively, enhance the ability of attenuating electromagnetic wave, and at the same time, make the impedance matching with air to the most extent, this paper mixed ferrite magnetism microwave-absorbing agents with semiconductor particulates. We got the effective EM parameter of the mixture using effective EM parameter model, and then analyzed absorption properties. As the result, it figured out the cubage proportion and conductance of semiconductor particulates based on the resistance matching principle. Through calculating the reflection ratio、impedance matching characteristic and attenuation coefficient of the material, it is proved that mixing ferrite magnetism microwave-absorbing agents with semiconductor particulate which has less permittivity could reduce real complex permittivity and increase imaginary complex permittivity of the composite material. It was able to enhance the ability of attenuating electromagnetic wave, improve absorbing properties, and meanwhile do not destroy the impedance matching characteristic with air.

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