Overall Electromagnetic Properties of Multifunctional Composites

Alireza V. Amirkhizi Postdoctoral FellowCenter of Excellence for Advanced Materials Department of Mechanical and Aerospace EngineeringUniversity of California at San Diego La Jolla, CA 92093 Abstract:Composite materials are used for their excellent structural performance. Load-bearing properties are traditionally the only aspects for which a composite structure is designed. Recent technological advances have made it possible to reach beyond this limited view. Inspired by biological systems, we seek to develop engineering materials that exhibit multiple functionalities in addition to providing structural integrity. I will present my research on embedding periodic arrays of scattering elements within composites to modify and tune their overall electromagnetic properties. A number of techniques for numerical and analytical modeling of the periodic media are discussed. Based on these methods we have designed and fabricated composites with tuned electromagnetic properties. Examples include fiber-reinforced polymer composites with embedded arrays of straight wires or coils. In both cases, the overall dielectric constant of the medium is reduced and can even be rendered negative within microwave frequencies. The coil medium can exhibit chiral response. Solutions for eliminating this behavior as well as a method for calculation of the bianisotropic material parameters are presented. One can achieve similar modification of the overall properties at higher frequencies by reducing the length scale. For example, we demonstrated that a polymer film with embedded nano-strips of gold can demonstrate negative dielectric constant in infrared regime. An example of a structural composite is fabricated and tested for which the magnetic permeability is altered and even turned negative. Finally, a general method for homogenization of the electromagnetic properties of periodic media based on the microstructure is presented.

Location: Stauffer Science Lecture Hall, Rm 102

Audiences: Everyone Is Invited

Contact: April Mundy