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Microwave Diagnosis of Carbon Black Rubber Compounds and Porosity Estimation in Composites

Published online by Cambridge University Press:  15 February 2011

Reza Zoughi
Affiliation:
Applied Microwave Nondestructive Testing Laboratory, Electrical Engineering Department, Colorado State University, Fort Collins, 80523 CO
S. I. Ganchev
Affiliation:
Applied Microwave Nondestructive Testing Laboratory, Electrical Engineering Department, Colorado State University, Fort Collins, 80523 CO
J. Bhattacharyya
Affiliation:
Applied Microwave Nondestructive Testing Laboratory, Electrical Engineering Department, Colorado State University, Fort Collins, 80523 CO
S. Gray
Affiliation:
Applied Microwave Nondestructive Testing Laboratory, Electrical Engineering Department, Colorado State University, Fort Collins, 80523 CO
D. Radford
Affiliation:
Applied Microwave Nondestructive Testing Laboratory, Electrical Engineering Department, Colorado State University, Fort Collins, 80523 CO
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Abstract

The results of an in depth study of the dielectric properties of various rubber compounds at different microwave frequencies are discussed. Subsequently, the influence of carbon black volume percentage on the dielectric properties of rubber is studied in a wide frequency range (5 -24 GHz). The results show that the real and imaginary parts of rubber dielectric constant increase as a function of increasing carbon black percentage. Frequencies around 5 GHz show more sensitivity to small changes in the carbon volume content. The presence of curatives in uncured rubber samples is detected, which is an indication of the sensitivity of microwaves to the chemical reaction triggered by these curatives. Similar approach is used to measure the air content in specially prepared model material (plastic microbaloon-filled epoxy) samples with varying degrees of uniformly distributed air inclusion. The results of these measurements for a wide range of frequencies is also reported. Measurement analysis resulted in detecting variation in the air volume fraction of around 1.5%. The results confirm the utility of microwave NDE techniques for local porosity detection and evaluation in dielectric composites.

Type
Research Article
Copyright
Copyright © Materials Research Society 1994

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References

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