A Comparison among Different Ways to Investigate Composite Materials with Lock-In Thermography: The Multi-Frequency...

Area of Science:

• Materials Science
• Non-Destructive Testing
• Mechanical Engineering

Background:

• Non-destructive testing (NDT) is crucial for early defect detection in aerospace structures to prevent failures.
• Active thermography offers contactless, fast, and cost-effective material inspection.
• Lock-in thermography is a flexible NDT technique adaptable to low-cost setups.

Purpose of the Study:

• To introduce and evaluate a novel multi-frequency via software (MFS) approach for lock-in thermography.
• To assess the MFS approach's effectiveness in inspecting carbon fiber reinforced polymers (CFRP) with artificial defects.
• To quantitatively compare the MFS approach against traditional sine and square wave excitation methods.

Main Methods:

• Implementation of a multi-frequency via software (MFS) technique by superimposing two square waves at different frequencies.
• Inspection of a CFRP sample containing defects of varying materials, sizes, and depths.
• Application of lock-in thermography for defect visualization and analysis.
• Quantitative comparison of MFS with traditional sine and square wave excitation methods.

Main Results:

• The MFS approach was successfully applied to detect defects in CFRP materials.
• The study provided a quantitative comparison of the MFS approach's performance against traditional methods.
• Advantages and disadvantages of the MFS approach were identified through comparative analysis.

Conclusions:

• The multi-frequency via software (MFS) approach shows potential for enhanced defect detection in CFRP using lock-in thermography.
• Quantitative comparison provides insights into the MFS method's efficacy relative to conventional techniques.
• Further research can optimize MFS for broader NDT applications in aerospace and other industries.