Identification of the Defect Type in Epoxy Resin Using the Differences in Reflected THz Wave Characteristics

A non-destructive inspection method by using Terahertz wave is effective for detecting defects in epoxy resin, which is widely used for insulating materials. To identity the type of defect such as metal fragment, void and resin burr is important to improve the electrical insulation property of the resin. In this study, we investigated the good method to identify the defect type by using THz time domain spectroscopy. As the results, we focused on the three feature properties of reflected wave: amplitude difference, frequency dependence and distribution of time interval. It is concluded that the combination of these feature quantities provides a useful way to distinguish the defect types.