Russian researchers combine ultrasonic, vibration and heat for composite flaw detection

Thanks to their high strength to weight ratio, composite materials are increasingly widely used in a range of sectors (particularly automotive and aerospace). But with even tiny defects leading to potentially disastrous consequences, there is a pressing need for increasingly accurate monitoring and testing methods. "Every year, new composite materials appear and they challenge existing methods of non-destructive testing. Joints between the materials are of particular complexity and importance", explained project manager Daria Derusova.

Whilst ultrasonic and X-ray testing are currently widely used at the production stage, X-Ray techniques are not always ideal for larger components, whilst ultrasonic facilities consume kilowatts of electricity to stimulate materials with a mono-frequency acoustic signal.

The TPU method uses uses piezoelectric transducers to carry out resonant ultrasonic stimulation as well as scanning laser Doppler vibrometer and an infrared camera. “The idea of the system is that a tested object….is exposed to acoustic stimulation in a wide range of frequencies,” said Derusova. “Elastic waves create vibrations of both material itself and its in homogeneities. The resonant frequency of vibrations of defects’ walls differs from that of the object that can be detected with a scanning vibrometer. In addition, due to intense resonant vibrations defect areas are locally heated. We register these changes with an infrared camera. The data of quality testing allow us to identify a defect itself, its location, form, and size,” he added.

Derusova said that the approach will consume less electricity than high-power ultrasonic installations and will offer an alternative to the existing methods of non-destructive testing. The group now plans to build a laboratory facility to test large and complex objects by form.