Analysis Of Vibration And Shock Response Of Sandwich Structures With Square Honeycomb Core

Sandwich structures have been widely used in aviation, marine and civil engineering due to their light weight, high strength to weight ratio, high stiffness to weight ratio, and excellent shock resistance, heat insulation and sound insulation. Because of the diversity and complexity of the structure form, the mechanical behaviour of sandwich panels has been one of hot spots that mechanics workers study.Based on analyzing and summarizing the existing theoretical methods, some new research methods are proposed to study the mechanical performance of sandwich structures with square honeycomb core. And the conceptive research on the new application of the sandwich structures in engineering are performed. The main works presented in the thesis are as follows:(1) By taking sandwich plate with square honeycomb core as a composite structure of plates and beams, the discrete characteristics of the sandwich plates are taken into account, which is different from the existing method of homogenizing the core. And the energy principle is used to obtain the governing equations of the bending response of the structure. The displacement of the sandwich plate is represented by double Fourier series and the Galerkin approach is utilized to solve for the governing equation. Numerical simulations of the clamed and simply supported square-honeycomb sandwich plates are performed, and the results obtained from the proposed method are compared with ones from the finite element analysis.(2) In this study, the free vibration and buckling response of sandwich plates with square honeycomb core are investigated. Based on the classical model of sandwich plates and Hamilton's principle, the motion governing differential equations of the square-honeycomb sandwich plates are derived, which consider the geometry characteristics of the face sheets and the core. The semi-analytical solutions of the natural frequency and the critical pressure of global buckling for simply supported square-honeycomb sandwich plates are obtained by using Fourier series and the Galerkin approach. The results from the present methods are compared with those obtained from the finite element analysis. Meanwhile, the effects of some geometrical parameters of the sandwich plates including cell size, core web thickness, core height and face sheet thickness on the nature frequency and the global buckling are discussed.(3) The transverse compressive response of sandwich plates with square honeycomb core is studied by using the numerical simulations, in which the effects of the loading rate, strain rate, relative density of the core and the initial imperfection on the dynamic buckling are discussed. In this study, the response of the sandwich structure with square honeycomb core subjected to underwater shock loading is investigated, and the effects of the geometric parameters and material parameters on the impulse applied on the sandwich plates are discussed. And the impulse acquired by the sandwich plates with square honeycomb core subjected to underwater shock loading is estimated by using the lumped parameter model. The results are compared with those obtained by three-dimensional finite element simulation.(4) Using energy conservation and rigid-plastic material model, the theory analysis of dynamic plastic response of sandwich plates with square honeycomb cores subjected to shock loading is carried out. And the approximate formula estimating the permanent deformation of the clamped sandwich plates with square honeycomb cores under shock loading are developed. The results of the different examples from the finite element analysis are employed to validate the theory formula accuracy.(5) The new application of sandwich structures with square honeycomb core in engineering is explored, and a new structure form of the composite stiffened cylindrical shell with honeycomb core is proposed to improve the shock resistance. Numerical simulation is employed to investigate the shock resistance of the new structure, and the effects of the geometric parameters and shock environment on the shock resistance of the structure are discussed. Meanwhile, the comparison between the shock resistance of the new structure and that of the stiffened cylindrical shell with same weight are carried out.In this thesis, the mechanical behavior of the sandwich plates with square honeycomb core is investigated by using theory analysis and numerical simulation. Some new methods for analyzing the mechanical performance of the sandwich structures are proposed, and the useful conclusions are obtained. These methods and conclusions have reference value for the further research and engineering design.