## 3 3D DIC in Blast and Shock Loading
[52] conducted an experimental study into the loading of thin square aluminium plates, through an explosively driven shock tube (EDST) and free air blast. Initially, the authors used a 15 mm thick plate to determine the reflected pressure in the EDST, to validate the method of producing a shock loading. The authors show that the EDST was able to produce an improvement in the variability of the incident pressure measurements and impulse, when compared to free air blasts. In addition, the EDST was able to produce significantly higher incident pressure and impulse, than is possible with a free air explosion of the same charge size. After validating the EDST, [PERSON] et al. changed to a 2.5 mm thick aluminium plate and conducted DIC to determine the displacement, strain and strain rate. The authors used a pair of Photron Fastcam SA5 high-speed cameras (Photron USA, Inc., San Diego, CA, USA) running at 25,000 FPS, to obtain the imagery used in the 3D DIC. The authors validated the DIC measurements with strain gauges and found very good agreement between the two. The authors show that the aluminium plates exposed to free air blast underwent a response that is separated into three stages. The first stage is a compressive through-thickness stress wave that is generated by the interaction between the blast wave and the panel, inducing reaction forces in the fixed boundaries. The second stage is a transfer of momentum and kinetic energy to the panel. The reaction forces generate a stress wave that propagates from the boundaries to the centre of the panel. While propagating, the stress wave produces bending and shear deformations. This causes the panel to move in the z-direction, initially with a square-like shape due to the clamping frame, and proceeding to a circular profile when the maximum deflection point reaches the centre of the plate. The final stage is an elastic vibration and stabilizes in its final shape. Their results show that the loading time for an EDST pressure wave was higher than with the free air blast. There is evidence that the stress/strain propagation patterns are different between the air blast and EDST. The EDST produces a more localized effect, generating a stress/strain wave at the borders of the loaded area and propagating towards the edge and centre of the plate. In comparison, the free air blast causes the stress/strain waves to be generated at the edges and propagate towards the centre. In addition, the EDST provided better reproducibility in terms of distribution, also providing better symmetry, and magnitude of the loading [52]. [PERSON] et al. [53] examined the response of annealed glass panels with a polyvinyl butyl (PVB) interlayer to explosive charge in a free air blast. The annealed glass was comprised of two 3 mm thick plies of annealed glass with a 1.52 mm PVB interlayer. The air blast was created by either 15 or 30 kgs of an explosive, with a TNT equivalence of 1.09 and standoff distances of 13, 14 and 16 m. The authors used a pair of Photron S3 cameras (Photron USA, Inc., San Diego, CA, USA) at 1000 FPS to obtain the imagery for the 3D DIC. [PERSON] et al. took the blast experimental data to calculate the reactions of both the pre-cracked and post-cracked panels. Due to the different behaviour of the glass in the two situations, the authors employed separate approaches. For the pre-cracked panel reactions, the authors used finite element modelling to estimate the relative magnitude of the bending and membrane stress from the DIC data collected on the back face. The authors show that the trends of the FEA and the experimental deflections were similar in the range of interest. The comparison of measured and estimated failure deflections produced similar results for all experiments considered. In the post-cracked regime, the authors show that the stress-strain curve of the experimental data was very noisy. For two of the panel edges in their first experiment, data uncertainties prevented them from reliably estimating the material coefficients.