Dynamic Analysis Of Composite Beam Structure With Delamination

The development of science promotes the improvement in technology. With the lighter and larger of modern engineering structures, people have more and more requirements on the stability and reliability of engineering material performance. Owing to its own uniqueness and a series of advantages such as high strength-to-weight and high stiffness-to-weight, composite laminated beam structure has been widely used in fields such as civil engineering. However,since the composite material is composed of a multiphase material, hence, it is easy to produce delamination during its production and use. The existence of delamination will lead to the weakness of the structure's carrying capacity and the degradation of its stiffness,thereby affecting the security of the structure and the life-span of the system. Therefore, the study of nonlinear composite beam structure with delamination has important significance and reference for the rational design of engineering structures and reducing the impact of nonlinear factors on structures.Firstly, the composite beam with a symmetrical delamination position is processed partitionedly in the present dissertation. Based on the basic theories of elastic mechanics,mechanics of composite materials and nonlinear mechanics, the differential motion equations of the delaminated beam are established. Moreover, the effect of different laying angles,different delamination depth, different lengths and different delamination paving material of beams with delamination on free vibration frequencies and modes of the beams is explored.Secondly, nonlinear motion equations of composite laminated beams with delamination are established by applying the Reissner variational principle and Galerkin's method. The modal eigen functions of the beam, the variable separation method and the multi-scale method are adopted to solve the nonlinear ordinary differential equations. Moreover, the nonlinear amplitude-frequency characteristics of the laminated beams with delamination are explored in the present dissertation. And the effect of different delamination lengths, delamination depth,laying materials and the external incentives on the primary resonance, ultra-harmonic and sub-harmonic resonance frequency of the beams with delamination is explored and discussed.Finally, the fourth-order Runge-Kutta numerical method is adopted to study the main resonance of composite beams with delamination under different parameters. And the bifurcation diagrams of beams with delamination changing with the variation of the incentive amplitude under different delamination lengths and different delamination depths are discussed respectively, as well as the Poincare map in chaotic motion, phase plane trajectories and time course curve waveform. The present study also reveals the law of the system into bifurcation and chaotic motion.