Study of the skin depth and defect detection in carbon fiber composites with Terahertz waves

As a new detection technology of composite materials, terahertz (THz) techniques have great advantages over other traditional detection methods. However, the application of this technology to the analysis of carbon fiber composite materials is limited. To solve this problem, the formula of THz wave skin lightening for carbon fiber composites was derived, and the conductivity and skin depth of the carbon fiber composites were calculated by using THz time-domain spectroscopy (THz-TDS). Finally, defect detection and imaging were performed on the sample. The results showed that defects could be detected effectively only if the sample thickness was less than the skin depth. For the first time, this study provides a quantitative explanation for the limitations of defect detection in carbon fiber composites using THz techniques. In addition, a method for calculating the conductivity of carbon fiber composites based on THz-TDS is proposed, which broadens the research methods for analyzing the electromagnetic properties of composites.