Buckling of non-uniformly distributed graphene and fibre reinforced multiscale angle-ply laminates

Present work investigates the biaxial buckling of three-phase, angle-ply laminates reinforced with graphene platelets and carbon or glass fibres. The analysis is based on Classical Plate Theory with the shear effect neglected. The laminate is defined as a three-ply symmetric laminate with simply supported boundary conditions and with different graphene and fibre contents in the surface and middle layers. As such, the laminate has a non-uniform distribution of the reinforcements in the surface and middle layers. Thicknesses of surface and middle layers are also non-uniform, but symmetrical. The objective is to investigate the effect of having a higher content of graphene and fibre in the surface layers as compared to the middle layer and also the effect of the relative thicknesses of the surface and middle layers on the buckling load. The main idea is to produce a cost effective design by concentrating the reinforcements in the surface layers where they are most effective. Thickness of the surface layers can be specified as the minimum required for a given buckling load to reduce the cost and to keep the volume content of the expensive reinforcements to a minimum. Effective properties of the three-phase composite are determined via micromechanical relations. Cost-effective designs using the minimum amount of reinforcements for a given buckling load can be determined from the graphs in the numerical results section. It is observed that relative graphene and fibre contents and thickness ratios of surface and middle layers affect the buckling load at different degrees. It is also observed that higher fibre contents can lead to lower buckling loads if the graphene content exceeds a critical value.