3D printed accordion-like materials: A design route to achieve ultrastretchability

Abstract

Brittle polymers suffer from the lack of stretchability, which limits their application when large deformation is required. To address this limitation, we investigate the stretchability of a set of cellular materials with conventional and novel cell architectures through 3D printing, experimental testing, and computational simulation. The presence of sharp corners restricts the stretchability of the honeycomb and arrowhead cellular architectures. A new class of accordion-like cellular architecture with sinusoidal struts is designed to enhance the planar stretchability of cellular solids. These accordion-like sinusoidal architectures exhibit an enhancement in the stretchability of the cellular materials even for those samples fabricated from brittle polymers. The manufacturability of the proposed architectures is demonstrated utilizing SLA and FDM additive manufacturing techniques. We customize the 3D printing settings to fabricate specimens with tailored architectures for experimental testing. Comparing the stress-strain curves obtained by experimental testing on the 3D printed samples with numerical simulation confirms that the failure strains for sinusoidal architectures can be as high as 20 times that of conventional honeycombs without compromising the energy absorption efficiency of the cellular materials. The stress-strain curves for 3D printed samples fabricated from flexible polymers are presented to show that energy dissipation in a hysteresis loop also can be enhanced by exploiting the accordion-like sinusoidal architectural designs. The sinusoidal struts in accordion-like cellular architectures offer a design route to extend the material property chart to achieve ultrahigh stretchability in lightweight 3D printable brittle and flexible polymers for applications that require combined stretchability, lightweighting, and energy absorption such as soft robotics, stretchable electronics, and wearable protection shields.