Additive Manufacturing of Kirigami Metasurfaces

Kirigami- the Japanese art of paper cutting – is used extensively as a design philosophy for stretchable and morphable structures. An array of cuts on a thin planar sheet creates a structure that can morph into a 3D pattern on applying an in-plane uniaxial load. This type of structure is called a kirigami metasurface. A subset of this type of structure is a buckling-induced kirigami metasurface that displays an in-plane and out-of-plane deformation response when an in-plane tensile load is applied. This metasurface type is multistable and displays a snap-through behaviour. The angles at which the cuts are made are one of the main influences behind the proportions of these in-plane and out-of-plane deformations.Cut patterns for these kirigami metasurfaces are specified with respect to the loading direction. For example, linear cut patterns contain periodically spaced linear cuts perpendicular to the loading direction, and angular cut patterns contain periodically spaced angular cuts in the form of the legs of an isosceles triangle, with its median parallel to the loading direction.Traditionally, stiff materials with low operating strain ranges are used to manufacture angled cut pattern kirigami metasurfaces. This work incorporates the use of high-toughness thermoplastic elastomer and fused filament fabrication (FFF) to manufacture metasurfaces with higher operating strain ranges. The influence of varying the cut pattern's geometric parameters on the metasurface's overall mechanical response is studied. Digital Image Correlation is used to quantify this out-of-plane mechanical response, and the effects of manufacturing using FFF on the bistability of the kirigami metasurface are analysed.The results showed that the 30-degree angled cut design gave the highest out-of-plane displacement relative to the size of its spikes. This angled cut design gave also gave the highest projected area amongst the other angled cut design types. The maximum projected area of this 30-degree angled cut design is 2.9 times greater than a similarly sized linear cut sample. An outcome of this work is to be the starting point for the use of FFF additive manufacturing and its design and material deposition freedom to tailor the response of the unit cells of an angled-cut kirigami metasurface. It also highlights the potential for using the angled cut design over the linear cut design for aerodynamics applications where local drag generation is favourable.Aerospace Engineering | Structures and Material