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 behaviour 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.
Highlights
The conventional wisdom in terms of the perception of structural instabilities has been that they are best avoided in practice
It is noteworthy that the cell elements bend immediately under loading and there are some differences in the initial stiffness of the cells
Since rectangular beam sections have been selected with constant depth and differin√g thicknesses,√the beam cross-section radius of gyration Rg = Ib/Ab = t/ 12
Summary
The conventional wisdom in terms of the perception of structural instabilities has been that they are best avoided in practice. With the rapid emergence of nonlinear mathematics, computational power, alongside numerical, and manufacturing techniques, the exploitation of the geometrically nonlinear range is becoming increasingly feasible for a wider range of applications (Reis, 2015; Champneys et al, 2019). In the fields of mechanical and aeronautical structures, instabilities have been used in so-called smart shape-morphing materials and structures that switch from one geometric form to another under particular loading ranges (Arena et al, 2018); this has significance in the field of energy harvesting (Hu and Burgueño, 2015). In the design of metamaterials, the nonlinear behavior of their internal structure can result in some rather unexpected but potentially exploitable features (Bertoldi et al, 2017)—this is especially the case for auxetic materials that are designed to have a negative Poisson’s ratio (Masters and Evans, 1996; Bertoldi et al, 2009; Grima et al, 2009; Körner and Liebold-Ribeiro, 2015; Hunt and Dodwell, 2019).
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