Nonlinear elastic wave propagation and breathing-debond identification in a smart composite structure

This paper addresses a problem on geometric-nonlinearity, due to the occurrence of breathing-debond in a smart composite structure (SCS). In order to solve the problem, elastic wave propagation based numerical simulations and laboratory experiments were carried out on SCS with baseplate – stiffener debonds. The frequency-domain analysis of the numerical and experimental signals shows that the presence of breathing-debond produces a prominent nonlinear response in terms of higher-harmonics. It was also noticed that the magnitudes of those harmonics significantly change with the increase in propagation distance. A baseline-free online breathing-debond source localization strategy is proposed that exclusively uses the changes in second harmonic magnitudes of the elastic wave signals registered at the sensor-networks in SCSs. The study was further extended for variable debond sizes and locations. It is observed that the proposed monitoring strategy is capable of localizing a wide range of breathing-debond sources in the SCSs.