A Microwave Time Reversal Algorithm for Imaging Extended Defects in Dielectric Composites

The expanding demand for glass fiber composites in aerospace, automotive and civil infrastructure industries has led to large-scale manufacturing and deployment of these materials. This has motivated the development of new nondestructive evaluation techniques that can detect critical damage modes and continuously monitor structural integrity. The advantages of microwaves for signal propagation and resolution in dielectric materials have previously been exploited. However, work has been largely limited to detecting well-confined, non-extended defects. In this paper we demonstrate the feasibility of a microwave time reversal algorithm for imaging extended defects in dielectric composites with the aid of computational simulations. We introduce an improved process for combining time-resolved information from multiple sources to image extended defects. Model-based numerical results from parametric studies indicate that our proposed algorithm can successfully resolve the location and spatial dimensions of different types of defects such as sub-surface voids, oblique cracks and metal-composite disbonds. The algorithm provides the computational foundation for the development of a new microwave nondestructive evaluation method for imaging challenging defect scenarios in dielectric composites.