3.2.3. Energy absorption capability

circumferential and longitudinal directions are presented in Figure 19. Both circumferential and longitudinal nodes for the front and back face-sheets have the similar deformation trend. At ~300 μs, all the nodes, except the node C5, have the maximum transient deflections, and then the deflection of these nodes decreases obviously due to the rebound of the elastic

Figure 19. Deflection variation of key points on the face-sheets of the curved sandwich panel. (a) Circumferential (front face-sheet), (b) circumferential (back face-sheet), (c) longitudinal (front face-sheet), and (d) longitudinal (back face-sheet).

Figure 18. Locations of the circumferential and longitudinal nodes on the face-sheets.

136 Contact and Fracture Mechanics

Figure 20 shows the histories of plastic dissipation of the components of a curved sandwich panel (R250-h0.8-C10-r15%-B3) subjected to blast loading. In the early stage of the response, the front face-sheet compresses the aluminum foam core, resulting in core crushing and significant energy dissipation. It can be found from Figure 20 that most of energy is dissipated by the large deformation of front face-sheet and core compression and core constitutes a major contribution, which is about 60% of total dissipation.

Effects of the impulse level and geometric configuration on the energy absorption of the components of the curved sandwich panels were indicated in a stack bar diagram in Figure 21. The partition of energy absorption of specimens is compared and analyzed in terms of the impulse level (specimen nos. 1–3), face-sheet thickness (specimen nos. 4–6), and core relative density (specimen nos. 7–9). The increase of impulse leads to a rise of total plastic energy dissipation in the specimens. Most of energy dissipation is attributed to large plastic deformation of front face-sheet and core compression. The energy absorption does not present a monotonic relationship with the face-sheet thickness. The specimen with 0.8-mm-thick facesheets has the best energy absorption performance, followed by that of 0.5-mm-thick facesheet, and the worst is that of 1.0-mm-thick face-sheet. This can be explained as follows: the

Figure 20. History of plastic dissipation of sandwich specimen during plastic deformation.

response process, back face-sheet deflection response, and energy absorption capability were explored. Experimental results show that permanent central point deflection linearly increases with blast impulse for all the specimen configurations and blast resistance of specimens can be enhanced by increasing the face-sheet thickness or the core density. The weaker blast resistance of R = 250 mm curved sandwich panels, compared to monolithic plates with the same mass, and the R = 500 mm sandwich panels, which are attributed to the different dominant deformation mechanisms. Simulation results present that the deformation modes, deflection responses, and energy absorption capability of curved sandwich panels are related with the loading intensity and geometric configuration. Energy absorption capability of curved sandwich specimens is monotonically increasing with the increased blast impulse and decreasing with the increase of core relative density. However, it does not monotonically change with the face-

Single-Curvature Sandwich Panels with Aluminum Foam Cores under Impulsive Loading

http://dx.doi.org/10.5772/intechopen.70531

139

The reported research is financially supported by the China National Natural Science

1 State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu, China

[1] Ashby MF, Evans AG, Fleck NA, Gibson LJ, Hutchinson JW, Wadley HNG. Metal Foams:

[2] Lu G, Yu TX. Energy Absorption of Structures and Materials. Cambridge: Woodhead

[3] Gibson LJ, Ashby MF. Cellular Solids: Structure and Properties. 2nd ed. Cambridge:

[4] Deshpande VS, Fleck NA. Collapse of truss core sandwich beams in 3-point bending.

2 Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of

sheet thickness.

Author details

Technology, Taiyuan, China

Publishing Ltd.; 2003

Cambridge University Press; 1997

Lin Jing1

References

Acknowledgements

Fundation under grant number 11402216.

\*, Zhihua Wang<sup>2</sup> and Longmao Zhao<sup>2</sup>

A Design Guide. Oxford: Butterworth-Heinemann; 2000

International Journal of Solids and Structures. 2001;38:6275-6305

\*Address all correspondence to: jinglin\_426@163.com

Figure 21. Plastic energy dissipation by the components of curved sandwich panels.

curved sandwich panel with thicker face-sheets deforms smaller due to the relatively larger structural stiffness; however, the severe damage may occur at the thinner front face-sheet under the large blast loading. Moreover, the total energy absorption amount of the curved sandwich panels decreases with the increased core relative density. Compared to the sandwich panels with the 10% core relative density, those specimens with 15 and 20% core density display relatively smaller energy absorption values, by 3.95 and 8.3%, respectively. This is attributed that the core compression values decrease with the increased core relative density, and the dominant deformation/failure mode of curved sandwich specimens is converted from the local core compression to global bending deformation, resulting in a weaker energy absorption capability.

### 4. Conclusions

Single-curvature sandwich panels with closed-cell aluminum foam cores, which include two radii of curvature (i.e., 250 and 500 mm), three face-sheet thicknesses (i.e., 0.5, 0.8, and 1.0 mm), and six different arrangements of foam core layers, were tested under air-blast loadings of various magnitudes. A total of 48 curved sandwich panels were examined, and the typical deformation and failure modes and the quantitative blast impulse and specimen deflection results were obtained and discussed. Based on the experiments, the corresponding finite element simulations were conducted using LS-DYNA software. The explosion and structural response process, back face-sheet deflection response, and energy absorption capability were explored. Experimental results show that permanent central point deflection linearly increases with blast impulse for all the specimen configurations and blast resistance of specimens can be enhanced by increasing the face-sheet thickness or the core density. The weaker blast resistance of R = 250 mm curved sandwich panels, compared to monolithic plates with the same mass, and the R = 500 mm sandwich panels, which are attributed to the different dominant deformation mechanisms. Simulation results present that the deformation modes, deflection responses, and energy absorption capability of curved sandwich panels are related with the loading intensity and geometric configuration. Energy absorption capability of curved sandwich specimens is monotonically increasing with the increased blast impulse and decreasing with the increase of core relative density. However, it does not monotonically change with the facesheet thickness.
