Monday, 11 October 2004 - 9:15 AM

This presentation is part of : Active Materials

Composites with Negative Refractive Index, Thermal, Self-healing, and Self-sensing Functionality (keynote lecture)

Sia Nemat-Nasser, UC San Diego, UC San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0416

The electromagnetic response of structural composites can be tailored by incorporating within the material small amounts of suitably configured periodically distributed electric conductors to create distributed inductive and capacitive elements. Over wave lengths that are at least several times greater that the size of a typical electrically-conducting unit cell, the overall electromagnetic (EM) properties, i.e., electric permittivity and magnetic permeability, of the resulting composite can then be tuned to desirable values, resulting in composites with, for example, dielectric constant of 1 (i.e., transparent to that wave length), or even with negative index of refraction. For the matrix material, we are using a polymer in which microcracks can heal, reversibly and at the molecular level. The healing reaction is exothermic, and polymerization can occur at rather low external temperatures. The embedded conductive wires can also be used as resistive elements to heat the material, as sensing (with embedded sensors) to detect internal damage, and as electrical conductors to tune the electromagnetic properties of the system. The structurally-integrated embedded microsensors render the composite information-based, so that it can monitor and report on the local structural environment on request, or in real-time as necessary. At UCSD we have developed special experimental facilities and techniques for composite production and its electromagnetic, thermal, and mechanical characterization. We have demonstrated the process of self-healing and self-sensing, and have created various softwares to design, interrogate, and simulate the response of the resulting multifunctional structural composites. We are now moving toward active tuning of the EM response.

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