The experimental synthesis of biphenylene, a two-dimensional carbon allotrope, theoretically predicted in 1997, took place in 2021.

In this paper, natural frequency analysis of functionally graded graphene platelet (GPL) reinforced composite cylindrical panel is investigated. Halpin-Tsai equations are employed to obtain the mechanical properties of the structure. The linear three-dimensional elasticity theory based on the Hamilton principle and the numerical finite element method are used for obtaining the governing equations of motion. Four patterns of GPL distributions such as: FG-X, FG-V, FG-O and UD are assumed through the thickness of shell. The effects of various parameters such as different distributions and weight fractions of GPL, zigzag and armchair lay-up, geometry and different boundary conditions on the natural frequencies and mode shapes of shell have been investigated. The results indicate that the maximum and minimum natural frequencies belong to FG-X pattern and FG-O pattern, respectively.