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This finite element model includes only one region in the neighborhood of one “hinge”. The one “hinge” shown here consists of a relatively short axial region of the foldable/deployable rod. The “hinge” is the region where the finite element mesh is concentrated. In the “hinge” region the cross section of the rod consists of two opposing open curved shallow cylindrical sectors with free longitudinal edges. During folding and deployment of the “hinged” rod each of these two opposiing shallow cylindrical sectors behaves in a way similar to a relatively short portion of a tape measure with a shallow curved cross section being bent longitudinally in one direction or in the opposite direction, as shown in the next slide. An actual long deployable rod would have along its length many identical “hinges” separated by relatively long “rigid” 360-degree cylindrical shell segments.
This and the next four slides are from:
Sergio Pellegrino (Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, CA 91125), “Folding and deployment of thin shell structures”. Pellegrino writes in April 2015: “Last year I gave a series of lectures on the folding and deployment of thin shell structures, as part of a course at CISM (in Udine, Italy) on Extremely Deformable Structures organized by Davide Bigoni. These lectures provided an opportunity to revisit the work that I had done over a period of about 15 years, with many students and collaborators. My write-up of the lectures will appear as a book to be edited by Davide. There is also a downloadable pdf file on my website ( http://pellegrino.caltech.edu/publications.html )”
ABSTRACT: Thin shells made of high modulus material are widely used as lightweight deployable space structures. The focus of this chapter is the most basic deployable thin shell structure, namely a straight, transversely curved strip known as a tape spring. Following a review of the materials used for the construction of deployable thin shell structures, including constitutive models and failure criteria developed specifically for this type of structures, this chapter provides an introduction to the mechanics of tape springs and tape spring hinges. Finite element techniques to model deployable structures containing tape springs are presented and the ability of these models to accurately simulate experimentally observed behavior is demonstrated. These tools can be used to design structures able to achieve specific behaviors. As an example, the design of a two-hinge boom that can be wrapped around a small spacecraft without any damage, and can dynamically deploy and smoothly latch into the deployed configuration is presented.
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