Foam-filled sandwich panels are often used in construction due to their lightweight and cost-effective properties. However, they are susceptible to air pockets during manufacture, known as voids, which can grow into blisters and compromise structural integrity. The Darmstadt scientists' research focuses on the early detection of these voids to ensure the longevity and safety of these materials.

The team has developed an ultrasonic testing technique that works with air-coupled Lamb waves. This method enables the non-contact detection of internal cavities. Two set-ups were tested with frequencies of 40 kHz and 200 kHz. The 40 kHz setup penetrates up to 14 mm into the foam, while the 200 kHz setup penetrates only 2.5 mm, but offers better contrast in defect detection.

This non-contact method offers great potential for integration into production lines and improves quality control and efficiency in the manufacture of sandwich panels. The results pave the way for faster and more accurate detection of air voids, improving cost efficiency and significantly reducing the C02 fingerprint.