Fig. 3.

Stiffness characteristics of a sheet, a single tube, and a zipper-coupled tube. (A–C) Eigenvalue vs. configuration (percentage of extension) for the sheet, the single tube, and zipper-coupled tubes, respectively. The large bandgap from the zipper-coupled tubes is also verified with an FE model. (D–F) Seventh, eighth, and ninth deformation eigenmodes when structures are at 70% extension (undeformed outline in red). (G–I) Energy distributions for the sheet, the single tube, and zipper tubes, respectively. The energy distribution is presented as a bar graph indicating the percentage of energy in fold bending (F), panel bending (B), and panel stretching and shearing (S). Representative element energies are shown for modes 7 and 8 of each structure. For detailed energy presentation see SI Text, section S4 and Fig. S7.