High-Resolution Lamb Wave Inspection in Viscoelastic Composite Laminates

Lamb wave inspection is a promising structural health monitoring method for carbon fiber reinforced plastic laminates. The optimal design of the excitation waveform based on Lamb wave pulse compression is an effective way to improve the inspection resolution in elastic plates. However, due to the viscoelastic property of the composite materials, the material damping effect will influence the amplitude response of the output signals; thus, the current design strategy is no longer applicable. The purpose of this paper is to develop an excitation waveform design strategy based on pulse compression to meet the demands of high-resolution Lamb wave inspection in composite materials. Different parameters that affect the design of excitation such as material damping effect, amplitude response, relative frequency bandwidth, and the selection of excitation waveform are considered synthetically. In addition, an excitation waveform design strategy based on the corrected amplitude response is also established to eliminate the effect of material damping and thus achieve better detection resolution. Finally, an experiment was carried out on a quasi-isotropic composite plate. The experimental results validate the robustness of the amplitude response correction method and the effectiveness of the excitation waveform design strategy.