## 3 3D DIC in Blast and Shock Loading
The air blast was created with a 100 kg TNT equivalent charge, with a standoff distance of 15 m. [PERSON] et al. used a pair of Photron SA1.1 cameras (Photron USA, Inc., San Diego, CA, USA) operating at 5400 FPS to capture the high-speed imagery. The authors used the ARAMIS software (GOM GmbH, Braunschweig, Germany) package to process the 3D DIC data from the imagery. The authors show that the initial displacement and pull-out of the PVC and PMI panels were greater than the panel with SAN foam core. This indicates that the SAN foam core is more resistant to the momentum of the blast and suffers less core damage. Their results showed that around 75% of the PMI panel was damaged, with a mix of debonding and cracking. In comparison, the SAN panel suffered the least damage. In addition, the authors show that there is a trade-off between reduced panel deflection and damage [57]. [PERSON] et al. [58] used 3D DIC to examine the response of metal face sandwich plates to impact by a metallic foam projectile to simulate blast loading. The sandwich plates the authors used were made from PVC foam layers, with densities of 80 kg/m\({}^{3}\), 160 kg/m\({}^{3}\) and 250 kg/m\({}^{3}\), and 5A06 aluminium alloy face sheets. The authors created four configurations for the testing, with all of the configurations having 0.5 mm thick face sheets. The four configurations the authors reported on were: (I) a single layer of 250 kg/m\({}^{3}\) foam, (II) 160 kg/m\({}^{3}\) foam followed by 80 kg/m\({}^{3}\) foam, (III) 80 kg/m\({}^{3}\) foam followed by 160 kg/m\({}^{3}\) foam, and (IV) three layers of 80 kg/m\({}^{3}\) foam. To simulate a blast impact, the authors used a single stage gas gun to propel a metallic foam projectile, 30 mm in length, 40 mm diameter and a density of 350 kg/m\({}^{3}\), at the sandwich panels. The authors used both 3D DIC and a digimatic micrometer system to measure the permanent deflection. To capture the high-speed imagery, [PERSON] et al. used a pair of Photron Fastcam SA-Z cameras (Photron USA, Inc., San Diego, CA, USA) operating at 36,000 FPS to capture the images and the ARAMIS software (GOM GmbH, Braunschweig, Germany) to process the images for the 3D DIC. The results from the digimatic micrometer and the 3D DIC are in close agreement. The authors show that there were three stages of dynamic deformation: during the first stage the impact impulse transfers to the front sheet, giving it a velocity; while the core and rear sheet remain static, the second stage is where the core becomes compressed, as the impulse transmits through the core to the rear sheet, giving the whole plate a common velocity and the final stage, where the energy is dissipated and absorbed through bending and stretching. The 3D DIC shows that the maximum strain occurs at the centre of the rear sheet, indicating that tension-tearing deformation in the middle of that face sheet will be one of the major failure modes when the impulsive intensity increases. Their results demonstrate that low-density, but thicker, cores perform the best in reducing permanent deformation of the structure. In contrast, higher density, but lower thickness, cores perform best in protecting the structure from destruction. With mixed core densities, the descending order of core densities has an advantage in blast resistance [58]. [PERSON] and [PERSON] [59] examined the response of steel plates to close proximity air blasts. The test plates were made from 3 mm thick Domex 355 MC; a high strength, hot rolled, low alloy steel. The air blasts were created with a PE4 plastic explosive charge of masses between 10 g and 50 g and a standoff distance of 40 mm and 50 mm. The 3D DIC imagery was captured with a pair of IDT Vision NR4 S3 high-speed cameras (IDT Vision, Pasadena, CA, USA) and the DIC processing conducted with the Dantec Dynamics Istra 4D DIC software package (Dantec Dynamics, Skovlunde, Denmark). The authors reported that all of the plates exhibited plastic deformation, without any indication of tearing or shearing failure.