## 4 Experimental Results and Analysis
### Experimental Details and Guided Wave Dataset  
In the experiment, a deep-learning-based damage-detection method is used to identify damaged regions in a carbon fiber composite panel. Moreover, carbon fiber composite is used as a composite material in relevant experiments. The stacking sequence of the woven fabric panel is \([0/90]_{3}\), with a whole thickness of 3 mm. The material is T700 12k carbon fiber fabric, and its mass density is 1577.8 kg/m\({}^{3}\). As shown in Figure 6, our experimental setup is a self-developed integrated waveguide-based SHM system, which mainly contains both hardware and software. The structural damage of the composite structure is considered in the experiments. The sound-absorbing plasticine is stuck on the composite material plate to simulate damage in the composite structure. Moreover, it generates and receives the guided wave signal at the sampling rate of 12 MHz. The schematic of the testbed and sensor layout is shown in Figure 7. The dimensions of the composite plate testbed are (450 mm \(\times\) 450 mm \(\times\) 3 mm), as shown in Figure 7a. We consider an area with dimensions of (200 mm \(\times\) 200 mm \(\times\) 3 mm) as the region to be monitored. As shown in Figure 7a, the damage location is in the region enclosed by 10 Piezoelectric Transducers (PZTs), and in the experiments, we further divided this region into four parts for damage detection, which are D1, D2, D3, and D4. Then, the sound-absorbing plasticine is stuck on each sub-region randomly to simulate the structural damage in the composite plate, with only one damage occurring at a time. Then, the PZT sensor network is positioned on the surface of the square array damage monitoring region. This sensor network contained 10 circle-shaped PZTs and 90 propagation paths as shown in Figure 7b. Moreover, these 10 PZTs are used as both sensors and actuators. It is worth noting that when one PZT is used as an actuator/transmitter, the other PZTs are all used as receivers. The diameter of the PZT sensor is 6.25 mm and the thickness is 0.2 mm. The excitation signal is a five-cycle sinusoidal tone burst waveform modulated by a Hanning window with a center frequency of 100 kHz. The fundamental modes, both A0 and S0, are adopted at 100 kHz in the experiments. Moreover, the sampling rate is 12 MHz, as the sampling point is set as 8000, the acquired signal length is 666 us, and the same acquired signal length is chosen for different paths. A total of 90 intact signals and 4 \(\times\) 90 damaged signals are collected. Together, these samples form a dataset. In subsequent experiments, this dataset is randomly split into training and test sets in about a 7:1 ratio. In the case of damage-simulation experiments, sound-absorbing plasticine is chosen as a medium for simulating damage due to its mechanical properties that lead to attenuation and phase shifting of guided waves. The size of the selected plasticine is about 30 mm \(\times\) 30 mm \(\times\) 20 mm. Moreover, Figure 8a,c illustrates the measured signals (Lamb wave) before and after attaching sound-absorbing plasticine. Furthermore, their corre  
Figure 6: Experimental setup and testbed. Figure 7: (**a**) Sensor arrangement in composite plate testbed; (**b**) Signal transmission route in composite plate testbed. sponding scattering signals are shown in Figure 8b,d. There are significant differences among these scattering signals. Specifically, baseline signal and damage signals in different areas received by the PZT-6 and PZT-9 are shown in Figure 8, where Baseline represents the undamaged baseline Lamb wave signal and Damage1 and Damage4 denote the damage signals passing through D1 and D4 damaged area, respectively. In particular, as shown in Figure 8a, the baseline and damage signals are all transmitted by PZT-1 and received by PZT-6 before and after damage, respectively.