Nondestructive Inspection and Quantification of Select Interface Defects in Honeycomb Sandwich Panels

Area of Science:

• Materials Science
• Non-Destructive Testing
• Composite Materials

Background:

• Honeycomb sandwich panels offer high strength-to-weight ratios for industrial use.
• Defects at the core-facesheet interface impair load transfer and panel efficiency.
• Existing non-destructive testing methods primarily focus on defect detection, not quantification.

Purpose of the Study:

• To develop and validate a high-frequency ultrasound testing (UT) method for detecting and quantifying defects in carbon fiber honeycomb sandwich panels.
• To assess the performance of UT using both laboratory immersion and portable single-side access systems.
• To evaluate the method's capability in identifying various defect types and sizes, including those below current detection limits.

Main Methods:

• Utilized high-frequency ultrasound testing (UT) with single-side access.
• Employed two testing approaches: a laboratory immersion tank and a novel portable UT system.
• Tested coupons with manufactured defects (missing adhesive, foreign objects, damaged/removed core) ranging from 5 to 40 mm.
• Developed an algorithm to quantify defect geometry and perimeter.

Main Results:

• Successfully detected and quantified defects with an average diameter error of 0.6 mm (immersion) and 1.1 mm (portable).
• Achieved high accuracy for missing adhesive defects (0.3 mm error).
• Quantified missing or damaged honeycomb defects with an average error of 0.7 mm, significantly below the 15-25 mm detection limit of existing methods.

Conclusions:

• High-frequency UT is effective for detecting and quantifying defects in carbon fiber honeycomb panels.
• The developed method surpasses current inspection capabilities for small and complex defects.
• This technique enhances the assessment of structural integrity and manufacturing quality for composite sandwich panels.