PSI - Issue 80

Haomiao Fang et al. / Procedia Structural Integrity 80 (2026) 53–64 H. Fang et al./ Structural Integrity Procedia 00 (2025) 000 – 000

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2. Fundamentals 2.1. Lamb wave propagation

Lamb waves, also known as plate waves, are a type of elastic wave which propagate in thin plates or shells, guided by the free upper and lower surfaces [23]. In the context of a finite medium, lamb waves exhibit infinite wave modes, with propagating characteristics that vary with incident angle, excitation frequency, material property and structural geometry. 2.2. Dispersion curves Lamb waves exhibit dispersion, which means their phase and group velocities depend on both wave frequency and plate thickness [24]. This phenomenon, known as dispersion, is influenced by the geometric and material properties of the plate or structure through which waves propagate. The dispersion relationship can be numerically expressed by (1): ℎ = (1) The relationship between the phase or group velocity of Lamb waves (or wavenumber) and the corresponding frequency can be described by a dispersion curve. In this study, the calculated results of IM7/8552 composite laminates using Dispersion Calculator (DC) [25] are depicted in Figure 1. Besides, the material properties of the layered thermoset material IM7/8552 unidirectional carbon fiber prepreg with a quasi-isotropic stacking sequence [0/45/−45/90] 2 are given in Table 1. Table 1: Material properties of IM7/8552 composite laminates. [ / 3 ] 1 [ ] 2 [ ] 12 23 12 23 [ ] 1590 171.42 9.08 0.32 0.5 5.29 3.974 2

Figure 1: The results of the dispersion curves in propagation angle 0° : (a) group velocity, (b) phase velocity, (c) wavenumber. In this study, the A0 mode exhibits dominant responses and greater sensitivity to surface damage within the low frequency range compared to the S0 mode. As a result, an excitation frequency of 50 kHz is selected, where dispersion is minimized and the A0 mode can be clearly distinguished from other modes.