*3.1. Experiment Setup*

The experiment setup is shown in Figure 3, including a 600 mm × 600 mm × 2 mm cross-ply glass fiber reinforced composite plate with unknown material properties. The thickness of each ply is 0.125 mm and the ply sequence is [02/904/02]S. The integrated structural health monitoring scanning system (ISHMS) is adopted as the monitoring system. This system is developed to control the excitation and sensing of the PZT sensor array. As seen in Figure 3, the array used in the experiment is a ULSA bonded on the structure surface with seven PZT sensors. The diameter of the PZT sensor is 8 mm. These sensors are arranged with a space of 10 mm and are labeled as PZT1–7, respectively, from the left to the right, where the length of the sensor array *L* is 60 mm.

Ten low-velocity impacts with a 2 J energy are performed at various positions on the structure shown in Figure 3. These impacts are induced by an impact hammer. The sampling rate is set to be 2 MHz and the trigger voltage is set to 3 V in the experiments. The sampling length is 10,000, including 2000 pre-trigger samples.

**Figure 3.** Experiment setup, ULSA arrangement, and impact applied positions (mm).
