Time-Domain Analysis of Microwave Signal Propagating Along FRPM Pipe Walls and Application to Nondestructive Inspection

We propose a method for the nondestructive inspection of fiberglass-reinforced plastic mortar (FRPM) pipes by the guided-mode propagation of microwaves along the wall of an FRPM pipe. We also report a new time-domain analysis for the guided-modes propagation of microwaves. By using this analysis technique, we identified the paths of the guided-mode microwaves that were propagated along the FRPM pipe wall and successfully identified the position of a foreign object located on the outside surface of the FRPM pipe. This analysis method is useful for the nondestructive inspection of underground FRPM pipelines, we believe.

I. Introduction

Fiberglass-reinforced plastic mortar (FRPM) is used in many fields as pipelines for agriculture, sewerage, and power cable protection [1]. FRPM is a composite material formed from fiberglass-reinforced plastic and mortar. These pipelines have a reasonably long lifetime when periodically inspected because of the inherent mechanical and chemical stability of FRPM. However, inspecting the underground FRPM pipelines is expensive as operations would need to be suspended.