## 4 Comparison with Experimental Results  
In this section, the group velocity computed from WFE is compared with experimentally determined group velocity values for a 2 mm thick CFRP laminate \([+45/0/-45/90/+45/0/-45/90]_{s}\). The composite laminate is composed of unidirectional T800S carbon fibre/epoxy laminae with the material properties described in Table 2. The dimension of the plate is 200 by 200 mm.  
The excitation signal was generated from the TG5011 waveform generator and amplified by the Ciprian amplifier. The pulse generator settings were set to a single cycle sine burst centred at 100 kHz for the first test (Figure 7) and 200 kHz for the second test. The experimental setup is shown in Figure 8. The output of the amplifier was split using a T-junction. One output was directed toward the excitation piezoelectric transducer, while the other was attached to the Picoscope signal acquisition system to act as a trigger. The second transducer was also connected to the Picoscope, which received the signal with a sampling frequency of 10 MS/s. All the data were stored in a laptop with the Picoscope 6 program installed. The waves were excited from the centre of the plate and received on a circular boundary 50 mm from the central point of excitation, as shown in Figure 8a. The circular boundary had sensing points in 15\({}^{\circ}\) intervals. The group velocity for the fastest wave mode at this frequency (i.e., S\({}_{0}\)) was calculated by the time of flight (ToF) method. The ToF of the S\({}_{0}\) wave was determined by measuring the difference between the time the signal was transmitted and received by the transducer. The ToF and and known distance were used to calculate the velocity of the wave at that given point. The tests were repeated 10 times and the average values were computed. The pointwise difference between simulation and experimental data was calculated and found to be less than 5% for all observation points. The results are shown in Figure 9. Notably, the experimental approach used in this research is the simplest method to calculate the group velocity and is limited to the fundamental S\({}_{0}\) mode. More advanced techniques are available that can robustly capture higher-order modes such as the one presented in [13]. The WFE model is also an idealisation of the  
\begin{table}
\begin{tabular}{l l l l l l l l} \hline
**Young’s Modulus** & **Young’s Modulus** & **Shear Modulus** & **Shear Modulus** & **Fibre Volume Fraction** & **Poisson Ratio** & **Poisson Ratio** & **Density** \\ \hline \(E_{s}\)(GPa) & \(E_{m}\)(GPa) & \(G_{f}\)(GPa) & \(G_{m}\)(GPa) & \(V_{f}\) & \(v_{f}\) & \(v_{m}\) & \(\rho\)(kg/m\({}^{3}\)) \\ \hline
220 & 4.7 & 15 & 1.85 & 0.4 & 0.2 & 0.3 & 1500 \\ \hline \end{tabular}
\end{table}
Table 2: Material properties of the homogenized CFRP layer (subscript \(f\) refers to fibre and \(m\) refers to matrix) [39].  
Figure 6: Dispersion curves along the principal direction 1 of 0\({}^{\circ}\) lamina for \([0/90/0]_{s}\) laminate obtained using the FE (- -) and WFE (-) methods.  
physical specimen, which might have inherent manufacturing flaws, which is common for composite structures but is not represented in the FE model. Despite these challenges, the experimental and numerical results were found to be in good agreement.  
Figure 8: The experimental setup used for determining the group velocity in a composite plate.  
Figure 7: Single cycle sine burst excitation signal centred at 100 kHz.