## 3 3D DIC in Blast and Shock Loading
reached the conclusion that the present of the polyurea on the blast-receiving side, configuration (i), amplified the destructive effect of the blast, promoting the failure of the composite sandwich panels. In contrast, placing the polyurea layer on the side opposite the blast-receiving side has a significant positive effect on the panel's response to failure mitigation and energy absorption [42]. [PERSON] and [PERSON] [43] examined the performance of e-glass vinyl ester composite face sheet/foam core sandwich structures, subjected to compressive in-plane loading prior to shock loading. The skins were e-glass vinyl ester composite with a [0\({}^{\circ}\)/45\({}^{\circ}\)/90\({}^{\circ}\)/\(-\)45\({}^{\circ}\)] weave and a thickness of 3.8 mm. The foam core had a thickness of 25.4 mm. The authors used three in-plane compressive loads, 0 kN, 15 kN (corresponding to \(\sim\)20% critical buckling load), and 25 kN (\(\sim\)33% critical buckling load). The blast wave had a peak incident pressure of 1 MPa, with a wave velocity of 1000 m/s. To obtain the high-speed imagery for the 3D DIC, the authors used a pair of Photron SA1 cameras (Photron USA, Inc., San Diego, CA, USA) running at 20,000 FPS. To process the imagery, the authors used the VIC-3D software (Correlated Solutions, Inc., Irmo, SC, USA). The 3D DIC showed that the out-of-plane deflections for the case with no compressive in-plane loading and the 15 kN loading had comparable deflection, with the specimen with 25 kN of in-plane loading exhibiting higher deflections. The authors recorded a reduction in the in-plane stress, which corresponds to cracking in the core material, in the case with no in-plane loading. In comparison, the drop in the in-plane stress that corresponds to core cracking is significantly smaller and occurs significantly later in the cases with compressive in-plane loading. Overall, higher levels of compressive loading cause more damage in the front face sheet, larger out-of-plane deflection and higher in-plane strain on the back face sheet. This leads to the overall blast resistance of the sandwich composite being significantly reduced [43]. [PERSON] et al. [44] examined panels of 2024 T3 aluminium with curvature exposed to a shockwave from a 1D shock tube. The panels were 2 mm thick and had curvature of (i) infinite (flat plate), (ii) 304.8 mm and (iii) 111.76 mm radius of curvature. The high-speed imagery was captured by a pair of Photron SA1 cameras (Photron USA, Inc., San Diego, CA, USA) running at 20,000 FPS and was processed by the VIC-3D software package (Correlated Solutions, Inc., Irmo, SC, USA). The authors show that the deflection rate was approximately the same in all three panels, but the panels with curvature reached a higher deflection when compared to the flat panel. This was caused by the flat panel stretching more, which limits the deflection. The 3D DIC showed that the initial velocity was the same for all three panels, but the velocity in the flat panel decayed faster when compared to the other two panels. The out-of-plane acceleration was the highest for the plat panel and decreased for the panels with curvature, with (iii) having the lowest acceleration. The panel with the highest initial curvature, (iii), experienced the least plastic deformation. Given that this panel also had practically no yield line formation (when compared to the other two panels) leads to the conclusion that panel has the best blast mitigation properties [44]. [PERSON] et al. [45] examined the response of aluminium test plates to an air blast. The aluminium plates had a thickness of 3 mm and were made from EN AW-1050A H24 grade and was clamped to a steel frame. The explosive used to generate the air blast was a 40 g spherical shape of C4 plastic explosive with a standoff distance of 250 mm. The high-speed 3D DIC imagery was captured with a pair of Photron Fastcam Ultima APX-i2 (Photron USA, Inc., San Diego, CA, USA) running at 6000 FPS. No information was given about the software the authors used to process the high-speed imagery.