Non-Destructive Testing of a Fiber-Web-Reinforced Polymethacrylimide Foam Sandwich Panel with Terahertz Time-Domain Spectroscopy

Yu Liu ^1,2, Yefa Hu ^1,2,3, Jinguang Zhang ^1,2

⁰School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070, China.

Sensors (basel, Switzerland) +

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March 28, 2024

View abstract on PubMed

Summary

Terahertz (THz) time-domain spectroscopy effectively detects internal defects like pores and cracks in thick composite sandwich panels. This non-destructive testing method also accurately measures panel dimensions, paving the way for future on-site inspections.

Area Of Science

Materials Science
Non-Destructive Testing
Composite Materials

Background

Terahertz (THz) non-destructive testing (NDT) is valuable for inspecting dielectric materials.
Current THz NDT applications are limited to thin, simple structures.
Validation is needed for THz NDT in thicker, complex composite structures.

Purpose Of The Study

To evaluate the effectiveness of THz time-domain spectroscopy (THz-TDS) for detecting internal defects in fiber-web-reinforced polymethacrylimide foam sandwich panels.
To assess THz-TDS for dimensional measurements of these complex composite structures.
To propose a super-resolution method to enhance imaging resolution.

Main Methods

Fabrication of 20 mm and 30 mm thick fiber-web-reinforced polymethacrylimide foam sandwich panel samples.
Defect detection using THz time-domain spectroscopy (THz-TDS) system.
Application of various imaging algorithms (peak-to-peak, maximum-amplitude, minimum-amplitude, pulse-width, time-of-flight) for signal processing.
Implementation of a block-based super-resolution reconstruction method (SSSRGAN) to improve image resolution.

Main Results

The peak-to-peak-imaging algorithm demonstrated superior performance in defect visualization.
THz-TDS successfully detected pores (min. 3 mm), debonding (min. 3 mm), and cracks (min. 1 mm thickness).
Inclusions (0.053 mm thickness) showed poor detection but features were extractable.
Dimensional measurements of panel, foam core, and web exhibited high accuracy with errors under 0.870 mm and 0.270 mm for the tested samples.

Conclusions

THz-TDS is a viable technique for detecting internal defects and performing dimensional metrology in thick, complex composite sandwich panels.
The proposed SSSRGAN method effectively enhances THz image resolution.
Future advancements in portable THz devices could enable real-time, on-site defect detection and structural analysis.

Keywords:

fiber-web-reinforced polymethacrylimide foam sandwich panels imaging algorithm non-destructive testing super-resolution reconstruction terahertz