Detection and monitoring of delamination in composite laminates using ultrasonic guided wave

In is work, the delamination of composite double cantilever beams (DCBs) was detected and monitored using ultrasonic guided wave. The composite DCBs were prepared, and the experimental platform for damage detection based on ultrasonic guided wave was built up. The damage response signal was obtained from the composite DCBs by piezoelectric sensor (PZT). The signal was processed by Hilbert transform (HT), Fourier transform (FFT) and wavelet transform (CWT). The effective linear guided wave parameters and nonlinear guided wave parameters are extracted to characterize the delamination length. The experimental results show that the occurrence time and duration of high-order harmonics are related to the length of delamination. High-order harmonics are found in the response signal, which is due to the non-linear contact between the guided wave and the closed microcracks in the delamination region. It verifies that the main source of harmonics in the laminated composite structure is the non-linear acoustic contact.