The dynamical equations describing the free vibration response of debonded sandwich beams with a soft core are derived using the higher-order theory approach. The nonlinear acceleration fields in the core are accounted for in the derivations, which is essential for the vibration analysis of the debonded sandwich beams. A through-the-width interlaminar crack (debond) between the upper face sheet and the core is assumed to exist before the vibration starts and not to grow under oscillations. The numerical analysis based on the derived equations reveals that the small debonds cause significant change in the natural frequencies and corresponding vibration modes of the sandwich beams. The important practical consequence of the present work is that the vibration measurements can be successfully used in nondestructive damage warning systems to detect debonding in sandwich beams.
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