A new method to detect delamination in composites using chirp-excited Lamb wave and wavelet analysis

Lamb waves offer an efficient way for monitoring the structural integrity of large carbon fiber reinforced polymer (CFRP) structures. This paper presents a new method that is able to detect and assess delamination's length in anisotropic CFRP plates. It uses a chirp signal, which contains a wide range of frequencies, as excitation. Thus the material is interrogated by Lamb waves with various wavelengths. This method is based on that, for a specific delamination length, only some particular frequency components are disturbed. Simulation and experimental results show that the lowest frequency that is perturbed by a delamination decreases as the delamination length increases. Therefore, by observing which frequency components of the chirp-exited Lamb wave are disturbed, delamination length can be estimated. Wavelet analysis is implemented for better comparison of signals at multiple frequencies.