Application of Embedded Dual-Loaded Modulated Scatterer Technique (MST) to Multilayer Structures

Health monitoring of infrastructure and other critical components composed of complex composite materials is an important ongoing concern. The embedded modulated scatterer technique (MST) has shown potential for evaluating electrical (i.e., complex dielectric) properties of bulk materials. This paper investigates its potential utility for evaluating properties of layered composite structures. The approach is based on irradiating an MST probe with an electromagnetic wave. This incident wave induces a current along the length of the thin dipole probe as a function of its load impedance and the material surrounding it, including boundaries within a layered structure. Consequently, the MST sensor may be placed at a specific location or boundary such that the probe response can be monitored over time for critical changes in the geometrical or the material property of the structure. In order to use MST for evaluating important characteristics of layered structures, this application must be fully investigated, and its limitations established. This paper presents an inclusive study of the application of MST for the evaluation of layered materials through pertinent electromagnetic simulations as well as experimental corroboration of the simulation results. The experimental results show that embedded MST is capable of detecting boundaries between layers within a layered structure and is also sensitive to the distance to the boundary.