## 3 Component Tests
### Experimental Results
#### 3.3.2 Sandwich Panels  
Experimental data from the tests on sandwich panels subjected to the lowest load level, i.e., 10 bar firing pressure, are shown in Figure 10. None of the components failed in these tests. A comparison between the mid-point displacements for sandwich panels and skins only is shown in Figure 11a. In terms of the cross-sectional displacements, see Figure 10, the specimens behave similarly. When the shock wave impacts, the front skin is accelerated uniformly. As for the tests with skins only, the edges  
Figure 8: Displacement and pressure vs time (**top**) and displacement profiles (**bottom**) for tests on aluminium skins only. Figure 9: High-speed images of failure in test Sk_P15: (**a**) initiation of tearing along the vertical edges (t = 1.35 ms), (**b**) complete tearing along the vertical edges (t = 1.75 ms), (**c**) tearing starts in the upper horizontal edge (t = 2.16 ms), and (**d**) complete failure along the entire frame (t = 2.97 ms). of the sandwich components start to decelerate first, but with a less pronounced difference between the edges and centre before coming to rest with a shallower, more rounded, displacement profile than for the skins only. Figure 11: Mid-point displacement of the aluminium skins only and the sandwich panels at (**a**) 10 bar firing pressure, (**b**) 12 bar firing pressure and (**c**) 15 bar firing pressure. Solid and dashed lines are used for series 1 and 2, respectively. Figure 10: Displacement and pressure versus time (**top**) and displacement profiles (**bottom**) for tests on sandwich panels with 10 bar firing pressure. The maximum mid-point displacement for the XPS-250 sandwich component is over 20% higher than for the XPS-400 component, while the difference between XPS-400 and XPS-700 is only approximately 7%. This variation in mid-point displacements is not consistent with the difference in compressive strength of the cores. A possible explanation for this observation is that the maximum reflected pressures in these tests are not high enough to initiate proper collapse of the higher density cores. Figure 11(a) shows the recorded pressure-time histories at sensor S01 for all tests at 10 bar firing pressure. Here, a distinct reduction in the measured pressure is observed for the sandwich component with an XPS-250 core. As seen in Table 3, the maximum recorded pressure in sensor S01 was approximately 7% higher for the sandwich components with XPS-400 and XPS-700 as core materials than for the XPS-250 sandwich panels and skins only. This reduction in measured reflected pressure may be connected to the reduced displacement of the sandwich panels with XPS-400 and XPS-700 cores, i.e., the larger displacement of the skins only and XPS-250 sandwich panels causes a pressure reduction in front of the components due to FSI effects. Experimental data from tests on sandwich panels with 12 bar driver pressure are shown in Figure A1, and mid-point displacements are compared with the results from the tests on skins only in Figure 10(b). In general, the results are similar to those found for 10 bar firing pressure. However, the difference in maximum mid-point displacement is more consistent with the difference in core material compressive strength at this firing pressure. The displacement with an XPS-250 core does not increase much compared to the tests at 10 bar firing pressure, while the tests with skins only and XPS-400 and XPS-700 as core material show a significant increase in displacement. Thus, at this load level the pressure seems high enough to activate more of the higher strength core materials. The behaviour  
Figure 12: Measured pressure in sensor \(1\) for the aluminium skins only and the sandwich panels at (**a**) 10 bar firing pressure, (**b**) 12 bar firing pressure and (**c**) 15 bar firing pressure. Solid and dashed lines are used for series 1 and 2, respectively.