Fig. 4. A physical model of a metamaterial fiber.

(A) Measured (i.e., known) engineering stress in the fiber (σ_f) and estimated (i.e., theoretical) engineering stresses in the metal (σ_m), polymer bridges (σ_p), and encasing polymer (${\mathrm{\sigma }}_{\mathrm{p}}^{\mathrm{e}}$) as functions of macroscopic strain. (B) Estimated average strain in the polymer bridges (ε_p) and the encasing polymer (${\mathrm{\epsilon }}_{\mathrm{p}}^{\mathrm{e}}$) as functions of macroscopic strain. (C) Total measured length (L) of the fiber, along with estimated lengths of the metal (L_m) and polymer bridges (L_p), and estimated initial lengths of the polymer bridges (L_po) and encasing polymer (${\mathit{L}}_{\mathrm{p}}^{\mathrm{e}}$) all as functions of macroscopic strain. Estimated values are determined directly from the model (see all equations and full derivation in note S2).