## 1 Introduction  
Since its discovery in 2004 [1], graphene has gained huge amounts of attention from both research and engineering communities due to its superior mechanical, electrical and thermal properties [2; 3; 4]. Compared to carbon nanotubes (CNTs), graphene has a much larger surface area and comparable properties, and soon becomes an emerging reinforcement in composites [5]. [PERSON] et al. [6] found that the graphene/epoxy composite exhibits significantly higer tensile strength and Young's modulus than the epoxy composites reinforced with the same amount of CNTs. Later, other studies also revealed that the buckling behavior of the graphene/epoxy composite is vastly superior to the composites with CNTs reinforcements [7; 8].  
Recently, [PERSON] et al. [9] developed a pioneering new method of producing graphene in bulk--flash Joule heating, which can zap any inexpensive source of solid carbon, from food scraps to car tires, and turn it into graphene in less than one second, and will open up various new applications in engineering. Its outstanding tensile strength, Young's modulus, buckling behavior and a much larger surface area of graphene, together with the advent of bulk producing method [9], enable it to become a most promising reinforcement material. As a consequence, the polymer composites reinforced with graphene nanofilers have attracted extensive research interest [10].  
Functionally graded materials (FGMs) consist of two or more materials, in addition to the continuous variation in both composition and properties along certain directions. The material properties of FGMs can be tailored to meet the requirements in various extreme working conditions. Recently, the functionally graded graphene platelets (FG-GPLs) reinforced composites have attracted academic interest. [PERSON] et al. [11] analyzed the thermal buckling and post-buckling of FG-GPLs reinforced plates. Based on the Chebyshev-Ritz method, [PERSON] et al. [12] studied the buckling and free vibration problem in FG-GPLs reinforced porous nanocomposite plates. Based on the high-order shear deformation theory, [PERSON] et al. [13] performed analysis on the nonlinear vibration of FG-GPLs reinforced composite beams in thermal environments, [PERSON] et al. [14] studied the bending and vibration response of FG-GPLs reinforced rectangular plates for different substrates and thermal conditions both theoretically and numerically, and [PERSON] and [PERSON] [15] focused on the effect of thickness stretching on static and dynamic responses of FG graphene-reinforced plates. However, the higher-order theory is more exact and complicated; there is no experimental evidence that it is necessary to adopt the higher-order theory in FG-GPLs composites [16]. That is, it is sufficient to use the classical plate theory (CPT) or first-order deformation theory (FSDT) to analyze the graphene-reinforced composites.  
This paper analyzes the dynamic behaviors in the functionally graded plates reinforced with GPLs using the first-order shear deformation theory. The improved Halpin-Tsai micromechanical model and traditional rule of mixture are utilized to determine the effective material properties. The governing equations are constructed in the state space, and then solved using method of reverberation-ray matrix (MRRM) [17; 18]. With special formulation, MRRM can avoid numerical instability inherently even for high frequencies or big wavenumbers [19; 20]. Then a parametric study is conducted, the effects of the weight fraction, nanofiller size, distribution patterns of GPLs, the boundary conditions and aspect ratios on the dynamic behaviors of the FG-GPLs plates are studied in detail in the numerical examples.