The decomposition of guided waves overlapped in the time–frequency domain in composite materials

Abstract

Compared with traditional bulk wave detection methods, guided wave detection has higher efficiency and accuracy, and therefore has a wider range of applications. However, the guided waves have two inherent properties, namely dispersion and multimodality. In propagation, the various modes of guided wave signals are usually overlapped in the time–frequency domain, which greatly limits the applicability of ultrasonic detection. In this paper, the generalized dispersive mode decomposition method is introduced to separate the modes overlapped in the time–frequency domain in the composite materials. In the method, the overlapped modes in the time–frequency domain can be separated by estimating the group delay of corresponding dispersive modes without any prior knowledge. When the estimated group delay is equal to the true group delay, the corresponding mode is completely separated from the overlapped modes. The dispersion curves of the carbon fiber composite laminate with a determined propagation direction were reconstructed by employing a combination of the generalized dispersive mode decomposition and zero-crossing techniques. And the accuracy and effectiveness were further validated through comparison with the results obtained from empirical mode decomposition and independent component analysis. The proposed method presents a useful guideline for the mode decomposition in the carbon composites and helps detect the mechanical properties or defects of the composite materials.