Imaging of barely visible impact damage on a composite panel using nonlinear wave modulation thermography

Dimitrios Dionysopoulos, Gian-Piero Malfense Fierro, Michele Meo, Francesco Ciampa

Research output: Contribution to journalArticlepeer-review

52 Citations (SciVal)
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Thermosonics is a well-established non-destructive evaluation (NDE) technique that uses an infrared camera to visualise material damage by capturing the frictional heating at crack surfaces when the sample under inspection is vibrated. A high power ultrasonic horn is typically used to generate vibrations, which is pressed against the surface of the test component. However, the direct contact between the horn and the surface generates acoustic chaos and high-amplitude vibrations, which can lead to non-reproducible and unreliable measurements and, ultimately, they can harm the structural integrity of components. This paper proposes an alternative to thermosonics, here named as nonlinear wave modulation thermography, for the detection and imaging of material flaws on a damaged carbon fibre composite panel. This material inspection technology combines the concept of nonlinear wave modulation spectroscopy using dual excitation with contact piezoelectric transducers and thermographic equipment. Whilst nonlinear ultrasonic modulation was used to enhance the sensitivity to micro-cracks, an infrared camera was used for defect visualisation. A nonlinear narrow sweep excitation method was employed to experimentally identify the dual excitation frequencies that resulted in high-amplitude damage resonance effects causing frictional heat at crack surfaces. A laser vibrometry system was also used to create a spatial mapping of the amplitude of sidebands. Nonlinear wave modulation thermography has proved to successfully detect barely visible impact damage in composites in a quick and reliable manner, thus overcoming the limitations of traditional optical thermography and thermosonics.

Original languageEnglish
Pages (from-to)9-16
Number of pages8
JournalNDT and E International
Early online date12 Jan 2018
Publication statusPublished - 1 Apr 2018


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