Evaluating impact damage on carbon fiber-reinforced polymer plates utilizing zero-group-velocity Lamb waves

This paper presents an effective method for evaluating the impact damage of composite plates using zero-group-velocity (ZGV) Lamb waves. A finite element (FE) model of the carbon fiber-reinforced polymer (CFRP) plate is established to analyze in detail the propagation characteristics of the S1-ZGV Lamb wave mode with a specified propagation direction. The study investigates the changes in the S1-ZGV mode with varying damage levels, characterized by a decrease in elastic moduli. Results indicate that as the damage level increases, the corresponding S1-ZGV frequency and amplitude decrease proportionally. The spectral amplitude (SA) at the initial S1-ZGV frequency exhibits a consistent and significant decrease with increasing damage levels, offering a reliable method for accurately assessing damage in CFRP plates. Additionally, the S1-ZGV mode of the CFRP plate is experimentally excited using the pitch-catch technique with air-coupled ultrasonic transducers to explore the variations in the S1-ZGV mode with different impact damages. Experimental findings show that the SA of the S1-ZGV mode at the initial S1-ZGV frequency decreases monotonically and sensitively with an increasing number of impacts. These experimental results correlate with the FE analysis, validating the effectiveness of accurately evaluating impact damage in CFRP plates based on the SA of S1-ZGV modes.