Page 116 - MSAM-3-4

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

in a lower overall stiffness. In addition, increasing the • For the structures with the same relative density, an
number of beams effectively redistributes the applied load increase in the number of beams contributes to more
across more beams. As a result, each beam experiences a compliance due to higher degrees of freedom and
reduced portion of the total load, leading to a decrease more efficient stress redistribution. Under the same
in the overall stiffness of the structure. Meanwhile, a loading condition, the triple-beam structure is more
second snap-through could be observed from triple- resilient toward large deformation while maintaining
beam structures (green dashed squares in Figure 11B), its structural integrity.
which did not appear on the force-displacement curves of
double-beam structures. We also found that the increase Acknowledgments
of beam numbers from one to two gave rise to the presence This research is supported by the Lorenzo and Pamela
of snap-through, and the increase of beam numbers from Galli Medical Research Trust. The authors acknowledge the
two to three allowed a more pronounced negative stiffness support from the RMIT Centre for Additive Manufacturing.
phase.

From the analysis of stress distribution in FE models, Funding
the maximum stress experienced by elements in the triple- Not applicable.
beam structure is 21 MPa. To compare, the maximum
stress in the elements of the double-beam structure is Conflicts of interest
36 MPa. This suggests that the triple-beam designs are Phuong Tran serves as the Editorial Board Member of the
more flexible and compliant compared to the double- journal but did not in any way involve in the editorial and
beam designs with the same relative density. Under the peer-review process conducted for this paper, directly or
same loading condition, the triple-beam structures were indirectly. Separately, other authors declare they have no
found to be more resilient toward large deformation while competing interests.
maintaining their structural integrity.

4. Conclusion Authors’ contributions
Conceptualization: Changlang Wu, Phuong Tran
This work explored double curved beam elements in Formal analysis: Changlang Wu, Chenxi Peng
the design of compliant structures with recoverability or Investigation: Changlang Wu, Chenxi Peng
bi-stability. Design parameters, boundary conditions, and Methodology: Changlang Wu, Chenxi Peng
number of beams were studied with respect to structural Supervision: Phuong Tran, Erich Rutz
responses under compressive loading. Experimental
results were compared with FE simulations and analytical Writing–original draft: Changlang Wu
models to understand the reversible and bistable compliant Writing–review & editing: Chenxi Peng, Phuong Tran,
mechanisms. Herein, the following conclusions were made: Erich Rutz
• A higher h’ value (ratio of beam apex height to Ethics approval and consent to participate
thickness) results in a more pronounced snap-
through for structures under compression, allowing Not applicable.
more considerable deformation while maintaining
their ability to return to the initial configurations. The Consent for publication
high recoverability of proposed structures in Group 2 Not applicable.
provides an avenue for designing reusable energy
absorbers in civil engineering. Availability of data
• The positive structural stiffness and peak force are The data that support the findings of this study are available
positively correlated to design parameter l’ (ratio of from the corresponding author on reasonable request.
beam span length to thickness). The decrease of l’
strengthened the lateral constraints for the two ends References
of the beams, thereby contributing to bi-stability.
• A higher value of g’ (ratio of membrane length to beam 1. Hesselbach J, Raatz A. Pseudoelastic Flexure Hinges in Robots
for Microassembly. United States: SPIE; 2000. p. 157-167.
thickness) can provide more constraint of buckling
Mode 2 by transferring the rotational motion of either 2. Howell LL, Magleby SP, Olsen BM. Handbook of Compliant
beam center to the axial motion of the other beam Mechanisms. United States: John Wiley & Sons; 2013.
more effectively. By adjusting the membrane length, a 3. Chen Q, Zhang X, Zhu B. Design of buckling-induced
more controlled bi-stable mechanism can be achieved. mechanical metamaterials for energy absorption using

Volume 3 Issue 4 (2024) 15 doi: 10.36922/msam.4960