fig2

Figure 2. Mechanics of high mechanical performance of BC, which can achieve higher strength and higher toughness as the fiber diameter decreases. (A) Experimental stress-strain curves of cellulose nanopapers with different fiber diameters. The inset image compares the strength of cellulose nanopapers and CNT films made of nanomaterials with the same diameter (11 nm). (B) Fracture toughness of cellulose nanopapers relative to the radius of randomly oriented cellulose nanofibers (CNFs). (C) Relationship among the diameter, tensile strength, and toughness of nanopapers according to conventional and anomalous scaling law. (D) Alignment and connection of cellulose chains on the (110)-(110) interface. (E) Breaking and reformation of hydrogen bonds during shearing process at three locations, where cellulose chains are aligned at the beginning of the shearing (Location 1) through hydrogen bonds (blue), misaligned with hydrogen bonds breaking (blue), and the formation of new ones (Location 2) during the shearing and realigned (Location 3) by new hydrogen bonds (red) in the end at equilibrium. Variation of number (F) and energy (G) of hydrogen bonds during shearing at three locations. (H) Interface strength between cellulose nanofibrils under shear stress with (red) or without (blue) the reformation of hydrogen bond. (I) Energy variation relative to displacement of perpendicular sliding between two CNF fibers (green) or two single-walled carbon nanotube (SWCNT) bundles (blue). (J) Toughening ratio as a function of the CNF length. (K) Effect of cellulose diameter and length to fracture toughness. (A, C, G, I) Reproduced with permission^[18]. Copyright 2015, National Academy of Sciences. (B) Reproduced with permission^[23]. Copyright 2018, Elsevier. (D-F) Reproduced with permission^[25]. Copyright 2015, Elsevier. (H, J, K) Reproduced with permission^[26]. Copyright 2017, Elsevier.