Advanced Ultrasonic Inspection of Thick-Section Composite Structures for In-Field Asset Maintenance

Area of Science:

• Materials Science
• Non-Destructive Testing
• Composite Materials

Background:

• Glass fibre-reinforced polyester (GFRP) composites are increasingly used in demanding applications.
• Inspection of ultra-thick composite structures presents significant challenges for conventional methods.
• Developing reliable in-field inspection techniques is crucial for structural integrity.

Purpose of the Study:

• To evaluate the in-field inspection capabilities of advanced ultrasound for ultra-thick GFRP composites (20-100 mm).
• To determine the limitations of advanced ultrasonic detection for delamination flaws at various depths and dimensions.
• To assess the relationship between material thickness and flaw detection accuracy.

Main Methods:

• Utilized custom-moulded GFRP plates with calibrated delamination flaws.
• Employed full matrix capture (FMC) with total focusing method (TFM) using a 0.5 MHz linear array probe.
• Varied flaw through-thickness, part thickness, and in-plane dimensions to test inspection limits.

Main Results:

• Successful delamination detection up to depths of 74 mm in ultra-thick composites.
• Inspection capability reduced to 35 mm when delaminations exhibited surface-to-surface contact.
• Observed an inverse relationship between detection ability and plate thickness, with exponential decay in depth measurement accuracy.

Conclusions:

• Advanced ultrasound shows promise for inspecting thick composites, but performance degrades with increasing thickness.
• Effective inspection depth is influenced by material thickness and flaw characteristics, generally within 1-20 times the wavelength.
• Improvements in probe coupling and signal processing could enhance measurement accuracy for thicker sections.