This paper concerns the experimental analysis of nonlinear response features of audcomposite laminate plate for impact damage detection. The measurement procedure is based onudthe Scaling Subtraction Method (SSM) and consists in exciting the damaged specimen with twoudsinusoidal signals at different amplitude. The linearly rescaled response signal at low amplitudeudexcitation is subtracted from the response at large amplitude excitation to extract the nonlinearudsignatures. The latter are analysed in the time domain to infer the presence of damage. Resultsudare compared with frequency domain analyses using the nonlinear vibro-acoustic modulationudtechnique (NWMS). Changes in amplitude and phase as well as modulation effects of theudacquired responses are also monitored. Surface-bonded, low profile piezoceramic transducersudare used for excitation and sensing. Both measurements techniques are applied to detect barelyudvisible impact damage in laminate composite plate. Non-destructive penetrant-enhanced X-rayudinspections are carried out to characterize the extent of internal damage. The behavior of theudnonlinear features and the sensitivity of each technique are also investigated in the paper.
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