## 2 Description of the Experiment  
### Experimental Object and Characteristics  
Considering that it is difficult to carry out experiments on the surface of a cylinder, this study firstly simplifies the experimental object to a plate for simulation and testing. Through the preliminary design and improvement of the distributed network array on the plate, the subsequent signal acquisition and analysis experiments are carried out. After the experimental results of the plate are obtained, the experiment will be extended to curved surfaces and cylinders. The plate and corresponding sensors used in the experiment are shown in Figure 3.  
In this experiment, carbon fiber/epoxy resin matrix composites are used. The test structure is given by carbon-fiber-reinforced polymer (CFRP) plates with clearly defined geometry and piezoelectric transducers. Composite laminates are generally composed of many basic sub layers laid in different directions and superimposed. The adjacent sub layers of laminates are usually bonded by a thin adhesive layer. The composite winding layer can bear most of the pressure load, in which the fiber is the main carrier. The resin plays a bonding role on the fiber, and it also plays a role in distributing and transferring the load between the fibers. Therefore, we need to select high-strength and high-elasticity reinforcing fiber and resin with excellent performance to improve the bearing capacity of the structure. The details of the raw materials of the composite plate used in this experiment are as follows. The reinforcing material is T700 SC12K carbon fiber from Toray Corporation of Japan. The matrix material is epoxy resin and imidazole curing agent, whereas the main component of epoxy resin is bisphenol A epoxy resin. Three CFRP plates were manufactured for this study with the dimensions of 300 mm \(\times\) 300 mm and a thickness of 4.8 mm, and the paving method is [+45\({}^{\circ}\)/0\({}^{\circ}\)/\(-\)45\({}^{\circ}\)/90\({}^{\circ}\)]\({}_{68}\). According to the above stacking method, different perspectives are used for stacking, and the thickness of a single layer  
Figure 3: Photos of the composite material plate and layout diagram of sensors.  
board is about 0.2 mm. A total of 24 layers are laid in the whole. The first specimen, called \"Intact plate\", was used for acoustic field measurement and related parameter measurement under the condition of structural integrity. The second sample, called \"Hole plate\", was used to obtain the Lamb wave data in the case of hole defects in the plate. The third sample, called \"Crack plate\", was used to obtain the Lamb wave data in the case of crack defects in the plate. The elastic modulus and shear modulus of composite materials are anisotropic, so 9 elastic constants are needed to describe their mechanical behavior. These 9 elastic constants can be divided into 3 principal directions of elastic modulus (E), 3 principal directions of Poisson's ratio (v), and 3 principal directions of shear modulus (G). These 9 quantities constitute the main mechanical performance parameters of composite material plates in experiments. The mechanical property parameters of carbon fiber/epoxy resin matrix composite single-layer plate are shown in Table 1.