This paper presents an analytical model to investigate the static behaviour of sandwich plates comprised of two isotropic face sheets and a honeycomb core. Through-thickness transverse shear stresses were considered using a unified displacement field with which various plate theories were implemented, i.e., exponential, third-order, hyperbolic, sinusoidal, fifth-order, Mindlin, and the classic plate theory. The equilibrium equations of a simply-supported sandwich panel were derived using the principle of virtual work and Navier solution was obtained under static transverse loading. After validating of the model, various mechanical and geometrical parameters were varied to characterise the behaviour of the structure under regular and auxetic response. It was found that the auxeticity of the core strongly affects the mechanical response, e.g., in controlling deflection, in-plane anisotropy, and Poisson’s ratio. Cell wall angle was found to be most critical parameter that can be used to adjust anisotropy, out-of-plane shear modulus, transverse shear stress distribution, and deflection of the panel. Also the cell aspect ratio controls the sensitivity of the core response to other geometrical variations. In terms of the higher-order theories, the deflection-dependent parameter of the unified formulation seems to have more control of maximum deflection compared to independent rotations. Auxeticity of the core showed some benefits in controlling anisotropy, deflection and providing additional out-of-plane shear rigidity. Overall, since there is not one-to-one relationship between specific values of Poisson’s ratio, anisotropy, and shear rigidity, careful design considerations must be invested to obtain a correct mechanical response.@en

The type and loading level of oxygen-containing functional groups on graphene oxide (GO) nanosheets significantly affect the size and alignment of nanochannels formed between the GO nanosheets and the separation performance of laminar GO membranes. Here, we demonstrate how double-oxidation of GO leads to the higher surface charge of GO nanosheets, the formation of highly stable water-based GO solution, more-ordered deposition of GOs on the polyethersulfone membrane through the pressure-assisted self-assembly method, and the formation of highly durable GO membranes possessing smoother surface morphology and higher antifouling properties. A multi-technique investigation was applied to follow the physicochemical difference between GO and double-oxidized GO, and the physical stability and separation performance of the corresponding membranes using experimental and computational studies. The double-oxidized GO-based membranes provided a significantly high water flux of 230 L/(m2.h) in 2.5 bar transmembrane pressure, excellent rejection of 99.9% for methylene blue (MB) dye, and outstanding separation performance stability over time. In contrast, GO membranes showed rejection of 81.5% for MB, and their separation performance diminished significantly over time. The antifouling properties of double-oxidized GO membranes were substantially higher (∼ four times) due to their higher negative surface charge and smoother surface morphology. The density functional theory (DFT) was used to gain insight into the interactions between the functional groups and the reasoning for the higher mechanical stability of double-oxidized GO membranes. Results revealed that the formation energy of GO decreases by increasing the number density of functional groups. It was also found that a higher number of carboxyl groups at the edges of the double-oxidized GO leads to higher hydrogen bonding, higher binding energy, and a more stable GO-membrane structure.@en