Graphene oxide (GO) or reduced-GO offer excellent mechanical, electrical and chemical properties. Their nanocomposites have been increasingly explored for attractive applications in diverse fields. However, due to the flexible feature and weak interlayer interactions of GO sheets, flexural mechanical properties of GObased composites especially for the bulk materials are largely restrained, which would hinder their use in real situations. Here inspired by amorphous/crystalline heterophase features within nacreous platelets, we construct a centimetre-sized GO-based bulk, the building blocks of which consist of crystalline GO and amorphous/crystalline MnO2 phases adhered by polymer-based crosslinkers. The GO/MnO2 heterophase layers are stacked and hot-pressed with further crosslinking between the layers to form bulk artificial nacre. The resultant GO/MnO2-based layered (GML) bulk exhibits the highest flexural strength (up to 203.4 MPa) among all of GO-based bulk materials. Moreover, an excellent fracture toughness, a strong impact resistance and light weight are also achieved. Mechanical and simulation analyses corroborate that the highly ordered heterophase structure together with complex crosslinking interactions across multiscale interfaces, lead to superior mechanical properties. We expect that these results provide interesting insights into the design of structural materials and allow the use of high-performance GO-based bulks in engineering and military applications.
Biological staggered composites, like bone, nacre, and dentin, possess the superior capacity of energy dissipation than that of conventional materials. In these nanocomposites, different staggered microstructures are widely observed, for example, symmetric staggered structures with regular platelet layouts and asymmetric staggered structures with offset and stairwise platelet layouts. In addition, the thickness of platelets in these biological materials is at the nanoscale, and the distance between the adjacent ends of platelets is large enough in staggered structures, which indicates the interface effect and tension region cannot be ignored in staggered nanocomposites. In order to investigate the possible synergistic effect of the platelet layouts, interface effects, and tension region on the dynamic properties of the nanocomposites, a generalized tension-shear chain model (TSCM) with tension region (TR) is proposed. According to the analytical solutions derived, the staggered nanocomposites with optimal structures can be designed to obtain superior energy dissipation capacity. Considering different loading frequencies in natural environment, the optimal dynamic properties of nacre can be achieved with a regular staggering platelet distribution, while the optimal dynamic properties of bone can be achieved when the number of periodic stairwise staggering platelets is appropriately smaller. These optimal platelet layouts in nacre and bone are consistent with the experimental results reported in many literatures. Therefore, the energy dissipation capacity of staggered nanocomposites can be highly improved, based on the profound understanding of the damping mechanism in biological nanocomposites.
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