A vision-based damage detection technique was proposed for the identification of damages in composite honeycomb structures. The motion above the damage area extracted from the wave field image with the developed image decomposition and image signal processing method reveals rich information to determine damage severity.
The standing wave prevailed at its resonant frequencies above the barely visible impact damage (BVID) on the surface of a CFRP/honeycomb composite sandwich plate, which was excited by a Q-Switch Nd:YAG pulse laser system for generating a broad-band guided wave, and the wavefield was captured by a Laser Doppler Vibrometer (LDV). With the developed image processing technique, the wavefield image that contains incident waves, reflected waves and standing waves could be separated from different wavenumber vectors and propagating directions. Phases, orientations and resonant frequencies derived from the separated standing wave were taken advantage of, for either emphasizing or magnifying the motion and illustrating the modal behavior on the damage surface. The barely visible impact damage (BVID) of the composite structure was therefore “visible” with the developed technique.
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