Research On Dynamic Modeling And Vibration Analysis Of The Composite Damping Structures

With the development of modern shipbuilding industry and the application of lightweight structure,higher and newer requirements are put forward for the performance of constrained damping structures(CLD).The combination of advanced composite materials and damping materials has broken through the performance limitation of traditional constrained damping structures formed a new type of composite damping structure.Since this structure is mainly composed of damping materials,directional composite materials and functionally graded materials,its dynamic behavior is more complicated.In the dynamic analysis,it is necessary to consider not only the material properties of each layer,the lamination schemes,the boundary conditions,but also the influence of the temperature-frequency effect of the damping material,which requires modeling theory and solution method with better precision,higher efficiency and less use restrictions.However,how to accurately and efficiently model the composite damping structure that fully considers the influencing factors such as geometry,material and boundary is still a major problem.Therefore,it is of great practical significance to break through the limitations of existing modeling theories and solving methods and to establish a modeling theory and solving method that can be applied to arbitrary thicknesses,material types,layup schemes and boundary conditions and also can consider the temperature-frequency effects of materials.In this paper,the composite damping structure is taken as the main line of the research.Through the systemic study of the dynamic characteristics,the dynamic behaviors of composite damping structures are summarized,which provides important theoretical support for the design and practical application of the composite damping structuresAiming at the inaccuracy and inefficiency in general modeling theory of the composite damping structures,a layerwise zigzag model based on shear deformation theory is proposed The model assumes the displacement function of each layer separately,and describes the strain of each layer separately,which can effectively improve the calculation accuracy.According to the continuity condition between layers,the mutual equivalent relationship of displacements is found to reduce the number of assumed displacements,which can effectively improve the calculation efficiency.On the basis of the layerwise zigzag model,the quasi-three-dimensional modeling of the typical composite damping structure with thick core and thin faces is carried out.The feature of the modeling theory is to use the three-dimensional elastic theory combined with the classical shell theory to respectively model the thick-soft core and the thin-stiff faces which forms a method for accurately analyzing and predicting the vibration and damping characteristics of the sandwich structures.Aiming at the problem of solving the dynamics of composite damping structures with arbitrary boundary conditions,this paper combines the layerwise zigzag model and the generalized Fourier spectrum method to develop a unified approach for solving the dynamics of composite damping structures with arbitrary boundary conditions.Based on the Rayleigh-Ritz method,the approach uses the generalized Fourier spectrum method to parameterize the classical or non-classical boundary conditions,which avoids the repetitive calculation of the traditional solution method when dealing with the boundary conditions of composite damping structures.At the same time,assuming the improved Fourier spectral functions are the structural displacements,which makes it have high-order derivative when solving various dynamic problems of the composite damping structures and can quickly converge to the true and exact solution.This makes the generalized Fourier spectrum method has a high degree of universality in dealing with various boundary problems of the composite damping structures.The dynamic characteristics of the composite damping structure with functionally graded materials and directional composites are systematically studied by using the established layerwise zigzag model and the generalized Fourier spectrum method.With considering the frequency and temperature dependent damping model,the influence of the temperature-frequency effect of the damping material on the vibration and damping characteristics of the composite damping structure is deeply studied.Aiming at the less study of the stochastic dynamics of composite damping structures,a stochastic vibration model under stationary random excitation is established by the frequency response function and the theoretical method established in this paper.Based on the model,the stochastic vibration of the composite damping structure under stationary random excitation is fully studied.Based on the generalized Fourier spectrum method combined with the parameter perturbation theory,a solving method for the free vibration of the composite damping structure with random parameters is proposed.The influence of the randomness of the damping material parameters on the natural frequency expectation of the composite damping structure is studied.In order to further improve the dissipation efficiency of the composite damping structure,based on the idea of the acoustic black hole,the one-and two-dimensional macro-acoustic design of the composite damping structure is carried out.By applying the damping material to the acoustic black hole,the reduction of the concentrated energy is realized.Then,the passive energy dissipation of the composite damping structure is transformed to the active dissipation.Based on the vibration analysis model of the one-and two-dimensional acoustic black hole structures established in this paper,the research on vibration transmission characteristics,energy dissipation behavior and parameter optimization design of the acoustic black hole structure is carried out.