Buckling analysis of sandwich plates with functionally graded graphene reinforced composite face sheets based on a five-unknown plate theory

With the remarkable mechanical properties, graphene is considered to be one of the most ideal reinforcements for composite materials. However, the existing five-known plate models neglecting the compatible conditions of transverse shear stresses in the literatures might fail to predict the critical buckling loads of sandwich plates with functionally graded graphene reinforced composite (FG-GRC) face sheets. If the compatible conditions of transverse shear stresses are unable to be satisfied, the buckling analysis of FG-GRC sandwich structures will be significantly influenced by the sudden change of material characteristics at the interfaces between the core and the face sheets. Thereby, an improved five-unknown plate theory is proposed for the buckling analysis of sandwich plates with FG-GRC face sheets. The proposed theory can meet beforehand compatible conditions of transverse shear stresses at the interfaces of adjacent laminates and only contains five independent displacement variables. The three-dimensional (3 D) elasticity solutions, CUF solutions and the results computed by using other five-unknown models are selected to appraise the capability of the proposed model. Numerical results show that the proposed plate model can yield accurately critical buckling loads. In addition, the effects of graphene volume fraction, distribution pattern, lamination sequence, span-to-thickness ratio and aspect ratio on the critical buckling loads of the FG-GRC sandwich plates are thoroughly investigated.