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

with the presence of a beam in the shape of buckling Mode bi-stability could be realized by the deformation of one
3. According to the stress distribution within the structure, beam instead of relying on both beams.
there was no plastic deformation during the compression.
Therefore, it is demonstrated that Design No. 8 deformed 3.3.2. Comparisons among structures with various
into and remained at another stable configuration due to number of beams
its bi-stability. To investigate the influence of the number of beams, a
According to the theoretical model, the force- comparison between single, double, and triple-curved
displacement curve for a bistable curved beam is beams was made. To ensure comparability, the single and
characterized by a negative force region. However, it triple-curved beam structures were designed to obtain
was not captured during the experiment. This could be the same relative density as the double curved beam
a result of the misaligned compression plates during the structures. Force-displacement curves from the validated
experiment. As shown in Figure 10A, the minimum forces FE models are presented in Figure 11 for the structures
captured for Design No. 8 are very close to zero. However, with design parameter values: l’ = 60, h’ = 3, g’ = 1. As the
since the compression plates were not perfectly parallel, beam thickness of triple-beam structures is beyond the
the top plate always had contact with the top surface of manufacturing limit of the 3D printer in this study, results
the structure despite detachment from snap-through. are compared numerically.
Moreover, it should be noted that only the inner beams According to the force-displacement curves, a triple-
(the bottom beam of the top pair and the top beam of the beam structure yields smaller stiffness and lower critical
bottom pair) were deformed into buckling Mode 2 or Mode buckling force. With more beams, the structure gains
3. Meanwhile, the outer beams were straightened at the additional degrees of freedom, allowing it to deform more
horizontal level. It could be inferred that the outer beams easily in response to external loads. The compliance of
play an important role in providing horizontal constraints the structure increases, suggesting that it can undergo
for the inner beams. In addition, the recoverability or larger deformations for a given applied force and result

A B

Figure 11. Response of structures with various number of curved beams, obtained from FE models. (A) Comparison among single, double, and triple-curved
beam structures (with the same relative density) regarding force-displacement curves with the design parameters of l’ = 60, h’ = 3, g’ = 1. (B) Magnified
force-displacement curves for double and triple-curved beam structures. Green dashed squares highlight the second snap-throughs observed in triple-
curved beam structures.

Volume 3 Issue 4 (2024) 14 doi: 10.36922/msam.4960