Fig. 2.

Mechanical performance of the chambered cuttlebone structure under compression. (A) Stress–strain curves of 11 compression tests. (B) Snapshots of deformation stages corresponding to the black curve in A. (C) A typical period of the stress–strain curve exhibits three stages, namely, local penetration (LP), expansion (EXP), and densification (DENS). The red curve plots the relative density $\left({\rho }_d/{\rho }_s\right)$ of the damaged chamber during deformation. ${\epsilon }_{pp}$, ${\epsilon }_{vp}$: peak-to-peak strain and valley-to-peak strain in a stress–strain period. ${\rho }_s$ is the density of the constituent material. (D) Distributions of peak stress, ${\sigma }_p$, versus chamber height, $h_0$. (E) Distributions of normalized peak-to-peak strain, $n{\epsilon }_{pp}$, and normalized valley-to-peak strain, $n{\epsilon }_{vp}$, versus chamber height, $h_0$. (F) Energy absorption capacity (W) versus density $\left(\rho \right)$ for cuttlebone in comparison to representative synthetic foams reported in literature, including AlSi₁₀Mg open-cell foams (35, 36), titanium foams (37, 38), sintered fiber stainless-steel foams (39), carbon nanotube reinforced nanocomposites (40), stainless-steel foams (41, 42), carbon nanotube reinforced aluminum foams (43), nickel foams (44), Zn/Al/Cu alloy foams (45), and epoxy foams (46). The dashed lines represent different W/ρ values, and the shaded area highlights the standard deviation of W/ρ for cuttlebone. (G) Digital image correlation (DIC) results corresponding to the points marked in C. The deformation is mapped with Hencky strain.