Fabrication and experimental characterisation of a bistable tensegrity-like unit for lattice metamaterials

The peculiar nonlinear mechanical behaviour of tensegrity structures and their engineering applications have attracted considerable interest in the last two decades. However, the difficulties in their traditional fabrication and assembling methods represent current limitations to their widespread use. This paper presents a novel design and fabrication procedure for bistable tensegrity-like units. Starting from the classical triangular tensegrity prism and using stereolithography technology, a double tensegrity-like unit was designed and realised monolithically as a compliant mechanism. High repeatability of compression tests confirmed the activation of the designed bistable twisting mechanism in large displacements, proving that the bistability of a tensegrity-like unit with null selfstress and no cables can dependably be achieved. Numerical simulations showed that a reduced-order stick-and-spring model is able to provide predictions on the nonlinear mechanical behaviour of the unit in close agreement with experimental results. Low relative density and bistable characteristics make this type of tensegrity-like unit suitable to manufacture highly-customisable multistable metamaterials. The proposed procedure could be applied to transform and additively manufacture other types of tensegrity structures with different nonlinear responses into corresponding tensegrity-like versions.

Automated summary

This paper presents a novel design and fabrication procedure for bistable tensegrity-like units using stereolithography technology. The designed unit has successfully achieved bistability and demonstrated a reliable activation of the twisting mechanism in large displacements. Numerical simulations have shown close agreement with experimental results, validating the proposed stick-and-spring model to predict the nonlinear mechanical behavior of the unit. The low relative density and bistable characteristics of this type of tensegrity-like unit make it suitable for manufacturing highly-customizable multistable metamaterials.