**2. Experimental Procedures**

In the experimental setup, 76.2 mm × 25.4 mm × 3.175 mm borosilicate glass samples, 5 mm × 5 mm × 0.05 mm aluminum alloy 1100 foils, and 10 mm × 10 mm × 0.05 mm 304 stainless steel foils were used as transparent overlay, flyer, and base (target) plates, respectively. A very thin layer of black Rust-Oleum enamel aerosol paint was sprayed on one side of the flyer to serve as a sacrificial ablative layer, preventing the top surface of the flyer from melting. A small thin piece of a clear double-sided tape (slightly larger than the laser spot size) a ffixed the flyer (from its painted side) to the transparent overlay. Target foils were attached to a fixed metal specimen using clear tape along the opposite edges, as shown in Figure 1. To create a gap as the stando ff distance between the metal foils, thin glass coverslips were used as spacers. Stando ff distance was controlled by the number of glass coverslips placed between the transparent overlay and the fixed metal specimen. The transparent overlay and the glass spacers were attached to the fixed metal specimen using black tape wrapped around the entire sample on both ends, as shown in Figure 2c. The surface of the metal specimen was covered with black tape to prevent it from bonding with the base foil.

**Figure 1.** Schematic of the LIW setup and different stages of the experiment: (**a**) LIW components; (**b**) Laser impact; (**c**) Material jetting in the impact region; (**d**) Springback region and welded area. Note: Spacers are not shown.

**Figure 2.** Structure of a LIW specimen: (**a**) Schematic of the LIW specimen (top and side views); (**b**) Schematic of the LIW specimen (isometric view); (**c**) An actual LIW specimen after laser impact.

A Spectra-Physics Quanta Ray Pro-350 infrared laser system (technical specifications listed in Table 1), was utilized for LIW experiments. The laser beam pulse was characterized as depicted in Figure 3. The spatial profile of the laser pulse was measured using an Ophir SP928 high-speed camera utilizing the BeamGage® software. The temporal profile of the laser pulse was measured using an Ophir FPS-1 fast photodetector in conjunction with a Teledyne LeCroy Waverunner 204Xi DSO high-resolution oscilloscope. Measured spatial and temporal profiles of the laser pulse are shown in Figures 4 and 5, respectively.


**Table 1.** Laser parameters [37,38], with permission from ASME, 2019.

**Figure 3.** LIW and laser characterization setup. reproduced from [37], with permission from ASME, 2019.

**Figure 4.** Measured laser pulse spatial profile (assumed axisymmetric) [37,39], with permission from ASME, 2019.

**Figure 5.** Measured laser pulse temporal profile [37,39], with permission from ASME, 2019.

As can be seen in the earlier Figure 1a, the laser beam passes through the transparent overlay and ablates the sacrificial layer. Since a large amount of energy (2.5–3 J) is released in a very short amount of time (~17 ns) over a small area (0.08 cm2), the ablative layer reaches extremely high temperatures (above 10,000 ◦C [40]) and vaporizes instantaneously creating the plasma depicted in Figure 1b. The plasma continues to absorb the energy of the laser and further expands while entrapped in the confinement layer. This leads to the creation of a high-amplitude pressure load penetrating the flyer plate in the form of shock waves. Consequently, the thin flyer plate is launched with high-velocity distribution towards the target plate. In some cases, as reported in the literature [24,30–36], upon collision, bonding is not achieved near the center of the ablated spot since the impact angle is zero and the impact velocity is too great. Instead, the flyer plate (and sometimes also base plate depending on the boundary conditions) springs back. In addition, a jet of metal particles that separates from flyer and base plates is ejected at very high velocities (several thousand m/s), as depicted in Figure 1c. Away from the center point, the impact angle is gradually increased until it reaches the minimum required for a successful weld. Consequently, the welding process initiates and depending on the experimental conditions, flat and/or wavy interfaces can be observed along the weld interface.

After the LIW experiments were performed as described, the welded samples were cut along the centerline of the welds (see Figure 6) and both optical and scanning electron microscope images of the cross-section of the weld were obtained. Prior to cutting, the welded foils were buried in epoxy (poured), wherein the cured epoxy prevented unwanted damage and deformation during the cutting process. After cutting, to reduce the surface roughness of the cut cross-sections, the samples were polished using Allied MetPrep 3TM grinding machine. 6 μm and 1 μm polycrystalline diamond suspensions were used on Gold Label and DiaMat polishing cloths respectively. This was followed by using 0.04 μm colloidal silica suspension on a Final A polishing cloth.

**Figure 6.** The centerline of the weld.

To measure the strength of the welds, lap shear tests were performed at speed of 0.5 mm/min using a 500 N load cell on an Instron 5969 universal testing system. A schematic of the lap shear test setup is shown in Figure 7. The experimental results are discussed together with the results of the simulations, described next.

**Figure 7.** Schematic of the lap shear test.
