Impact response of metallic stacked origami cellular materials

• Published in: International journal of impact engineering Vol. 147; p. 103730
• Main Authors: Harris, J.A., McShane, G.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2021; Elsevier BV
• Subjects: Additive manufacturing; Auxetic materials; Blast; Buckling; Cellular materials; Cellular structure; Compressive strength; Energy absorption; Gas guns; Impact; Impact response; Impact tests; Impact velocity; Laser beam melting; Mechanical analysis; Origami; Selective laser melting; Stainless steels; Strain analysis; Strain rate sensitivity; Unit cell; Origami; Impact; Auxetic materials; Selective laser melting; Cellular materials; Additive manufacturing; Blast
• ISSN: 0734-743X; 1879-3509
• DOI: 10.1016/j.ijimpeng.2020.103730

•Stacked origami structures were fabricated from stainless steel using additive manufacturing.•Dynamic compression tests and numerical simulations were conducted to determine mechanical behaviour up to 150 m/s.•Auxeticity decreased with increasing impact velocity, and effectively disabled at 100 m/s.•Strength, energy absorption, and energy absorption efficiency increased with impact velocity.•Origami geometry allows for tuning of wall angle (and mechanical response) at fixed relative density. A greater degree of folding produced a softer mechanical response. Cellular materials are attractive for applications in structural protection and impact energy absorption. Progressive buckling of cell walls during compression delivers good specific strength and energy absorption. In a cellular solid, the arrangement of the cell wall material with respect to the direction of loading has a key influence on its mechanical response. This is especially true for cellular materials loaded in dynamic compression, where dynamic buckling and inertial stabilisation effects can also be sensitive to the alignment of cell walls with the loading direction. Origami-based geometries provide one route to designing cellular materials to achieve controllable collapse modes and, in some cases, auxeticity. The stacked Miura-ori geometry has been proposed recently as a strategy for constructing a volume of periodic cellular solid from an origami-inspired unit cell. However, these have been previously difficult to manufacture. Using selective laser melting, an additive manufacturing process, stainless steel stacked origami materials were produced in a periodic cellular arrangement for the first impact tests on such a cellular material. The origami specimens were tested with a gas gun and direct impact Hopkinson bar apparatus, at impact speeds of 50 m/s and 100 m/s. The auxetic behaviour of the origami fold was observed to diminish at the higher impact speeds, due to the localisation of deformation to individual fold layers. Different fold configurations were studied through simulations, with clear trends observed between fold angle and specific energy absorption and strength. Lastly, the influence of material strain rate sensitivity was investigated numerically.