Mechanical properties of structural biological materials.

(a) Mechanical property chart comparing the strength and modulus of twelve natural materials (see Box 1); (b-e) representative stress-strain curves of the four structural classes of materials. Notes: Guidelines shown in (a) are derived material indices for elastic hinges (σ/E) and springs (σ2/E) as defined by Ashby [4]. The icons in the upper-right corners of (b-e) indicate the modes of loading: tension, bending, or compression. Data used to create the figures are listed in S1–S6 Tables, compiled from numerous sources (see Supporting Information).