Free Space Microwave Non Destructive Characterization of Composite Materials
Jan Obrzut, Ahmed M. Hassan, Edward J. Garboczi
We present a free-space microwave experimental measurement system for the non-destructive testing of composite materials. The system operates in the Q- frequency band of 30 GHz to 50 GHz with fixed wave propagation distance between free-space antennas. Dielectric or conducting specimens either thinner or thicker than the microwave penetration depth can be analyzed. The error correction procedure for this system implements two reference measurements of complex scattering parameters. One reference is from a known conductor, such as an aluminum plate, and the other from a wave propagating in an air slab with a geometrical propagation length equal to that of the specimen under analysis. In order to illustrate the efficacy of our technique, we present the analysis of dielectric laminates, as well as of nano-carbon epoxy composites with inter-laminar multi-walled carbon-nanotube structures. These laminates can be microwave absorbing or reflecting, with inter-laminar carbon nanotube networks for enhanced strength-to-weight performance and electrical conductivity. During manufacturing, the carbon-nanotube network evolves from a non-conducting dielectric state through the conductivity percolation transition until the desired properties are obtained. Such changes in properties can be accurately captured by our error-correction model and measurement of the magnitude and phase of the scattering parameters. Compared to previously developed free-space techniques, the presented methodology is simpler, and therefore attractive for on-line non-destructive testing and quality control in the manufacturing environment.
Proceedings of the American Society for Non Destructive Testing, NDT of Composites 2015, May 4-6, 2015 Seattle, WA.
, Hassan, A.
and Garboczi, E.
Free Space Microwave Non Destructive Characterization of Composite Materials, Proceedings of the American Society for Non Destructive Testing, NDT of Composites 2015, May 4-6, 2015 Seattle, WA. , Seattle, WA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918256
(Accessed November 29, 2023)