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Materials Science in Additive Manufacturing Bistable 3D-printed compliant structure

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Figure 10. Structural response of Group 3 specimens under quasi-static compressive loading. (A) Force-displacement curves obtained from experiments
and numerical simulations for structures with different g’ values (left) and corresponding configurations after removing the compressive load (right).
(B) Structure deformations at point A (the 1 snap through) and point B (the 2 snap through) captured from experiment and FE models. The beams
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deformed into buckling Mode 3 shapes are highlighted using the red dash lines. Point A: first snap-through, Point B: second snap-through.
experienced more pronounced snap-through. This leads The deformation of the beams in Figure 10B explains
to distinctly different compliant behaviors from the three the transition between recoverability and bi-stability by
structures. The pictures in Figure 10A are the configurations varying the membrane length. Pictures of the specimens
of the specimens after removing the compression load. were captured from both experiment and numerical
Both pairs of the beams in Design No. 6 (g’ = 1) returned simulations, corresponding to point A and point B on the
to their original shapes, while that of Design No. 8 (g’ = 5) force-displacement curves (Figure 10B). As highlighted
remained stable at the final deformed configuration. For by the red dash lines, no obvious buckling Mode 3 was
Design No. 7 (g’ = 3), the bottom pair of the beams observed during the compression for Design No. 6 (g’ = 1).
recovered to their initial shape, and the top pair retained Instead, the bottom beam of the top pair deformed into
the deformed state. In other words, with the increase of the buckling Mode 2. Hence, the structure is expected to
the membrane length g, the compliant feature of the be recoverable according to the criteria in the analytical
structure transits from recoverable to half recoverable/half model. For Design No. 7 (g’ = 3), buckling Mode 3 was
bi-stable, and further to fully bi-stable. As the membrane found during the first snap-through, and buckling Mode 2
transfers the rotational motion to axial motion, the was captured in the second snap-through. This is attributed
longer membrane reduces more rotational motion at the to the phenomenon after removing the load, where the top
beam center. Therefore, buckling Mode 2 could be better half stayed at the deformed configuration and the bottom
suppressed with the increase of g’, which contributed to the pair of beams recovered to the original shape. As for
transition from reversibility to bi-stability. Design No. 8 (g’ = 5), both snap-through events happened

Volume 3 Issue 4 (2024) 13 doi: 10.36922/msam.4960