1. Introduction

Light-weight cellular metallic foams possess good multifunctional combinations of mechanical, physical, and electromagnetic properties including the high specific stiffness, high specific strength, and superior energy dissipation capacity by plastic deformation of their cellular microstructures [1–3]. Since they can undergo the large plastic deformation at a constant nominal stress, resulting in a relatively long plateau stress in their stress versus strain response history curves shown in Figure 1, metallic foams are continually used in energy absorbers for the protective purpose [3]. More commonly, the metallic foams are extensively used as the cores of

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Figure 1. Stress versus strain response curve of the aluminum foam with 11% relative density.

sandwich structures to enhance the blast/shock resistance performance. The sandwich structure typically consists of two thinner but stiffer face-sheets and a softer crushable core, which is a special topology form comprising a combination of different materials that are bonded to each other so as to utilize the properties of each component for the structural advantage of the whole assembly. The face-sheets resist nearly all of the applied in-plane loads and bending moments, while the core sustains the transverse and shear loads mainly. The employment of flatted sandwich structures (i.e., the beam and panel) to resist blast/shock loadings still remains academic and engineering interests, and the responses of these sandwich structures to various loading cases have been widely investigated [4–12]. Some representative failure modes (e.g., face-sheet yielding and core compression or shear) have been experimentally observed [5, 7, 9– 11], while the load-carrying capability and mechanisms of plastic failure and energy absorption have been predicted in theory and simulation [4, 6, 8, 12].

core using commercially available adhesive. Figure 2 shows the picture of single-curvature sandwich panels with two radii of curvature, that is, 250 and 500 mm. Three face-sheet thicknesses (i.e., 0.5, 0.8, and 1.0 mm) and three core relative densities (i.e., 11, 15, and 18%) were examined. The quasi-static mechanical properties of LY-12 aluminum alloy face-sheets with the density r = 2780 kg/m3 are Young's modulus E = 68 GPa, Poisson's ratio ν = 0.33, yield

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

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

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The core material was closed-cell aluminum foam, and the typical quasi-static uniaxial compressive stress-strain responses for three different relative foam densities are shown in Figure 3. Here, an energy efficiency-based approach is proposed to calculate the plateau stress and densification strain. Energy absorption efficiency η (εa) is defined as the energy absorbed up to a given

> Ð <sup>ε</sup><sup>a</sup> <sup>ε</sup>cr σ εð Þdε σ εð Þ<sup>ε</sup>¼ε<sup>a</sup>

where εcr is the strain at the yield point corresponding to commencement of the plateau regime. The densification strain ε<sup>D</sup> is the strain value corresponding to the stationary point in

The energy absorption efficiency curves of the aluminum foams are also depicted in Figure 3,

(1)

¼ 0 (2)

nominal strain ε<sup>a</sup> normalized by the corresponding stress value σ<sup>c</sup> (ε) [16]:

the efficiency-strain curve, that is, where the efficiency is a global maximum:

η εð Þ¼ <sup>a</sup>

dη εð Þ dε � � � � ε¼ε<sup>D</sup>

stress σfY = 310 MPa, and shear modulus G = 28 GPa.

Figure 2. Photograph of specimens with the two radii of curvature.

and the plateau stress is obtained from

Curved sandwich panels, which better combine the advantages of shell and sandwich structures, are envisaged to possess good potential in withstanding blast or impact [13–15]. However, studies on curved metallic sandwich structures appear quite limited to date. Consequently, a comprehensive study on blast-loaded single-curvature sandwich panels with aluminum foam cores is conducted in experiment and simulation.
