## 2 Description of the Experiment
### Experiment Design and Preparation  
Defect pre-setting is shown in Figure 5. The defects are set in the middle of the laminate, mainly including hole defects and crack defects. In this experiment, both hole defects and crack defects are preset in the center of the plate. The diameter of the hole is set to be 5 mm, with a depth of 3 mm. The size of the crack is approximately 1.5 mm \(\times\) 30 mm, with a depth of 1 mm. According to the previous statement, this experiment selects a center frequency of 210 kHz as the excitation frequency. Correspondingly, the sampling frequency for the time sequence signal in this experiment is chosen as \(9\times 10^{6}\) Hz, and the amplitude of the excitation signal is set to 1 mV. In this experiment, the excitation frequency of the guided wave signal is 210 kHz, and the longest time for the propagation of the guided wave direct wave signal in the structure is calculated to be 0.000058 s, based on the wave speed of the corresponding guided wave slowest mode at this frequency. Therefore, to ensure the complete acquisition of the guided wave signal, a storage time length of 0.0001 s, which is greater than this value, is selected for the signal automatic acquisition system. As the selected sampling point count is set to 5 \(\times\) 10\({}^{6}\) per second, 500 data points can be collected for each sensor path. This is then used as the window length for extracting a set of signal data. Each signal was taken as a whole set of data for subsequent training without being cut or segmented. The PZT sensor array is arranged symmetrically in the center, forming a square shape. The piezoelectric disk measures 8 mm in diameter. PZT sensors are arranged at four ends as excitation and reception sources.  
Figure 4: Ultrasonic excitation system equipment and experimental principle.  
All PZTs can be used as actuators and sensors in the experimental testing process. The PZTs are bonded to the surface of the composite plate using cyanoacrylate adhesive. Compared with other adhesives, this adhesive is more suitable for quickly bonding PZT sensors in short-term experiments. When pasting the sensors, keep the bonding surface clean and flat. As shown in the schematic diagram in the article, we sequentially numbered the PZT sensors as PZT1, PZT2, PZT3, and PZT4, and stimulated the excitation signal from PZT1 to PZT4 in turn. When each sensor is stimulated, the other three sensors receive the signal. Therefore, we can obtain 12 sets (4 \(\times\) 3) of Lamb wave signals in one monitoring experiment. First, ultrasonic nondestructive testing is conducted on the specimens to verify their intact state and obtain the signal data in the intact state. Multiple groups of one-dimensional time series signals under different defects are obtained by repeated experimental tests. By repeating the test in this way, multiple sets of signal data can be obtained, and the current data set constructed is 360 sets of signal data. These data constitute a large enough data set, which can reflect the main characteristics of this defect. This data set can be used for subsequent experiments and algorithm analysis to extract the features and signal information of corresponding defects.