### Experimental Results
#### 2.3.1 Plates Subjected to a Single FSP Impact  
For each test, the full-field out-of-plane displacement and the in-plane strain fields are extracted. Figure 4 represents a plane view of the aluminum plate specimens in configurations 1 and 2 after full FSP perforation. As a first observation, plugging failure is found as the predominating failure mode for all tests in both configurations. Because the plates are thin (2 mm), the FSPs with the lowest tested velocities accomplished perforation. Evaluation of the images obtained from HSC 1, as shown in Figure 5a, reveals that the FSP pitch angle both before and after the ballistic impact is low (Video S2). It is highlighted that no plastic deformation or visual damage occurs in all of the projectiles. Both configurations' penetration and perforation processes are recorded using HSC 2 and 3. It is shown that at the moment of impact, the FSP causes a localized bulge at the rear side of the plate as illustrated in Figure 5b. A localized shearing of material induced by the FSP front surface is created in the contact zone. Immediately after, the FSP penetrates, and a circular plug is punched through the plate, leaving a clean-cut hole. Subsequently, the punched plug can be seen attached to the front surface of the projectile as shown in Figure 5c. After that, the punched plug is separated from the FSP. The red circle in Figure 5c highlights the perforation hole. No significant differences in the failure mode are noticed between the different tests of each configuration. Figure 3: Out-of-plane displacements obtained after DIC calculations (configuration 2) using subset sizes of: (**a**) 9 and (**b**) 21. It should be highlighted that the FSP front surface cannot be captured by high-speed cameras 2 and 3 during impact due to the plug covering the FSP face. The FSP undergoes rotation from the moment it exits the launcher until it fully perforates the plate, which makes it challenging to determine the exact angle of impact. To address this, the high-speed images captured by cameras 2 and 3 are analyzed, and the front surface of the FSP is tracked at different time steps for each test of all configurations. Figure 6 provides an example for the second test of configuration 2. The red rectangle represents the FSP's front surface, and the angle \(\phi\) indicates the impact angle relative to the plate. Figure 4: Plane view of aluminum plate specimens (configurations 1 and 2) after full FSP perforation. Figure 5: (a) Image sequence of the ballistic impact event (configuration 2) captured by high-speed camera 1 at different time steps showing the penetration and the perforation process in the plate: (b) bulge created by the FSP at the rear surface of the plate at the moment of impact, (c) a plug punched through the plate after full perforation and flying together with the FSP. It is found that 12.7 mm size FSPs create larger local deformations. As an example, Figure 7 displays the 3D out-of-plane displacement field of the second test of configuration 2. The 3D out-of-plane displacement fields were extracted from the VIC 3D V8 software and exported as MATLAB figures. It is shown that the entire plate responds to the impact. However, the maximum displacement of 3.2 mm is exclusively observed in the immediate vicinity of the impact hole. It is highlighted that points placed at different orientations (0\({}^{\circ}\), 45\({}^{\circ}\), 90\({}^{\circ}\), 135\({}^{\circ}\), and 180\({}^{\circ}\)) from the center of the impact point exhibit different out-of-plane-displacements. Figure 6: High-speed imaging of ballistic impact (configuration 2) on plate target: tracking FSP front surface angle (image 1) and orientation (images 2 to 6) (Video S3). Figure 7: Configuration 2, test 2: 3D out-of-plane displacement of aluminum plate showing a local deformation around the impact hole. In Figure 8, the out-of-plane displacement of points located on three circles with a given radius (15 mm, 30 mm, and 45 mm) and centered on the impact coordinates are analyzed and shown for configurations 1 and 2.