Effects of Disruptive Inclusions in Sandwich Core Lattices to Enhance Energy Absorbency and Structural Isolation Performance

Abstract

The energy absorption and structural isolation performance of axially-compressed sandwich structures constructed with stiff face plates separated with an auxetic lattice core metamaterial is studied. Advances in additive manufacturing increasingly allow bespoke, carefully designed, structures to be included within the core lattice to enhance mechanical performance. Currently, the internal structure of the lattice core is deliberately disrupted geometrically to engineer suitable post-buckling behavior under quasi-static loading. The desirable properties of a high fundamental stiffness and a practically zero underlying stiffness in the post-buckling range ensure that energy may be absorbed within a limited displacement and that any transfer of strain to an attached structure is minimized as far as is feasible. It is demonstrated that such disruptions can be arranged to enhance the panel performance. The concept may be extended to promote cellular buckling where the internal lattice buckles with densification occurring at defined locations and in sequence to absorb energy while maintaining a low underlying mechanical stiffness.

Description of anisotropic material response of wire and arc additively manufactured thin-walled stainless steel elements

“…For isotropic materials, the Poisson's ratio must satisfy −1 < ν xy < 0.5; negative Poisson's ratios indicate 'auxetic' [46,47] materials, which exhibit transverse expansion under axial tension, while ν xy = 0.5 indicates incompressible materials, such as liquids. For metals, Poisson's ratios typically range between 0.25 and 0.35; for steel [48] and stainless steel [45], ν xy is commonly taken as 0.3.…”

Characterisation of the anisotropic response of wire and arc additively manufactured stainless steel

“…For isotropic materials, the Poisson's ratio must satisfy -1<𝜈xy<0.5; negative Poisson's ratios indicate 'auxetic' [29,30] materials, which exhibit transverse expansion under axial tension, while 𝜈xy = 0.5 indicates incompressible materials, such as liquids. For metals, Poisson's ratios typically range between 0.25 and 0.35; for steel [31] and stainless steel [32], 𝜈xy is commonly taken as 0.3.…”

Enhancing energy absorption through sequential instabilities in mechanical metamaterials

“…Although soft materials with a relatively high yield stress would technically be able to perform this task, examples of which are polymeric composites and foam-filled thin-walled structures [ 18 , 19 ], they require a significant volume or thickness of material to accommodate the large deformation required to absorb the required energy quantity; see figure 1 a , where δ 0 represents the necessary deformability for such a system to be effective. However, cellular structures with bespoke geometrical configurations can be designed with a high load-carrying capacity and minimal post-buckling stiffness [ 20 , 21 ]. This has the potential to achieve the same energy absorbency but for a fraction of the compression displacement δ 0 , as represented in figure 1 b .…”