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Published May 1, 2020 | Submitted
Journal Article Open

Temperature-induced shape morphing of bi-metallic structures


In this work, we study the thermo-mechanical behavior of metallic structures designed to significantly change shape in response to thermal stimuli. This behavior is achieved by arranging two metals with different coefficient of thermal expansion (CTE), Aluminum and Titanium, as to create displacement-amplifying units that can expand uniaxially. In particular, our design comprises a low-CTE bar surrounded by a high-CTE frame that features flexure hinges and thicker links. When the temperature increases, the longitudinal expansion of the high-CTE portion is geometrically constrained by the low-CTE bar, resulting in a large tangential displacement. Our design is guided by theoretical models and numerical simulations. We validate our approach by fabricating and characterizing individual units, one dimensional arrays and three-dimensional structures. Our work shows that structurally robust metallic structures can be designed for large shape changes. The results also demonstrate how harsh environmental conditions (e.g., the extreme temperature swings that are characteristic of extraterrestrial environments) can be leveraged to produce function in a fully passive way.

Additional Information

© 2019 Elsevier Ltd. Received 6 August 2019, Revised 3 October 2019, Accepted 23 October 2019, Available online 24 October 2019. This research was carried out at the California Institute of Technology and the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration, and funded through the President's and Director's Fund Program. S.T. acknowledges the support of Roketsan. P.C. and C.D. acknowledge support from the Foster and Coco Stanback Space Innovation Fund. The authors wish to thank Fernando Garza for his fabrication efforts, Christina Naify and Terry Gdoutos for useful discussions.

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