## 1 Introduction
Using high-strength composite materials, many researchers have tried to manufacture boring bars that could improve the dynamic stiffness and achieve large length/diameter (L/D) ratios without chatter. For example, [PERSON] et al. [21] designed four types of composite boring bars with differently shaped steel cores. Using the finite element method (FEM), they analyzed the performance of these boring bars. The results showed that a boring bar with a cross-shaped steel core exhibited the best cutting capability and stability. In particular, when L/D = 7.0, this kind of boring bar could achieve non-chatter cutting. [PERSON] et al. [22] designed and manufactured a carbon-fiber epoxy composite boring bar. Experimental results showed that the dynamic stiffness of this kind of composite boring bar was about 30% higher than that of a tungsten carbide bar. Furthermore, chatter did not occur when L/D = 10.7. Considering three different supporting conditions, fixed-free, pinned-pinned-free, and spring-spring-free, [PERSON] et al. [23] analyzed the dynamic characteristics and stabilities of composite boring bars. However, they did not consider the shear deformation and rotational inertia in analysis. According to this research, we can conclude that, using a kind of composite material to construct a boring bar for cutting does not require complicated control structures and is more practical than the first two categories. Therefore, the manufacture of composite boring bar is very promising. All the aforementioned studies neglected the influence of the shear deformation and rotational inertia, which should not be ignored in dynamic characteristic analysis of the boring bar (which is a kind of thick beam model). If the influence of shear deformation and rotational inertia is ignored in the calculation of nature frequency, the result will be much larger than the actual value [24]. That will lead to the inaccurate adjustment of the cutting speed and depth in CNC boring, and even destroy the surface finish of machined workpieces. Moreover, because of the high dynamic stiffness of the composite material, the study about the dynamic characteristics of the composite boring bar with shear deformation and rotational inertia is more conducive to improve the understanding about the inherent dynamic characteristics of the composite materials boring bar and to provide guidance for designing of boring bars. Therefore, this paper focuses on studying the influence of the shear deformation and rotational inertia on the dynamic characteristic of composite boring bar. In contrast to existing studies, the novel features of this paper are as follows. First, based on the Adomian Modified Decomposition method (AMDM), this paper presents a composite boring bar model considering shear deformation and rotational inertia. Secondly, the mode shapes of the established a mathematical model is compared and analyzed. Thirdly, the natural frequency and the cutting stability is compared comprehensively. In particular, the convergence about the chatter stability of our model is verified. The analysis results drawn in this paper are helpful to improve the understanding about the inherent dynamic characteristics of the composite boring bar, and to provide guidance for designing of boring bars. Moreover, to further improve the surface finish of machined workpieces, accurate adjustment of the cutting speed and depth in CNC boring can be designed based on the results drawn in this paper.