Experimental Study of Impact-Damage Detection in Composite Laminates using a Cross-Modulation Vibro-Acoustic Technique

The paper demonstrates the application of cross-modulation vibro-acoustic technique for impact-damage detection in composite laminates. A composite plate is monitored for damage resulting from a low-velocity impact. The plate is excited simultaneously with two harmonic signals: a slow amplitude-modulated vibration pumping wave and a constant amplitude-probing wave. The frequency of both the excitation signals coincides with the resonances of the plate. An electromagnetic shaker is used to introduce the pumping wave to the plate. Two surface-bonded, low-profile piezoceramic transducers are used for probing-wave excitation and measurement. The wave modulation is transferred from the pumping wave to the probing wave in the presence of impact damage. This effect is exhibited in a power spectrum of the probing wave by a pattern of sidebands around the carrier harmonic. The results show that the amplitude of the sidebands is related to the severity of damage. The study also investigates also the effect of boundary conditions on the results.