Research On Composite Sandwich Structure Based On Layerwise/Solid-Element Method

The layerwise/solid element method(LW/SE) was used to study the static and free vibration of sandwich structure under different boundary conditions. Dynamic substructure method which was based on LW/SE was introduced to study the free vibration of sandwich structure. Three following aspects were included in the specific research.First, LW/SE was proposed to analyze single sandwich structure. The layerwise theory was used to analyze the behavior of the facesheets, and the three-dimensional solid elements were employed to obtain the governing equations of the core. And then, based on the governing equations of the facesheets and core, the finial governing equation of sandwich structure was assembled by using the compatibility conditions, which was used to ensure the compatibility of displacements at the interface between facesheets and core. The numerical results of the proposed method were compared with those obtained from the 3D elastic model developed in finite element software MSC.Patran/Nastran, and good agreements are achieved. Furthermore, a series of numerical analyses were conducted to further explore the effects of thickness and composite of the facesheets on the static responses and free vibration responses of sandwich structures.LW/SE was used to analyze and establish the governing equation of sandwich structure with double-layer cores and multi-layer cores. In view of the complicated structure of double honeycomb sandwich structure, two local modeling were used to reduce the amount of calculation. The results were compared with the analysis of global modeling. A series of numerical analyses had proved that LW/SE can realize the reliable analysis of sandwich structure with multi-layer cores, and different ways of modeling were good for accuracy of calculation and reducing the amount of computation under different conditions. Finally, the static and free vibration analyses of composite sandwich structure with double-layer cores were made.Considering the complexity of the sandwich structure and large amount of calculation of free vibration characteristics analysis, The Fixed-interface Modal Synthesis Technique was introduced to analyze free vibration of sandwich structure. First of all, the governing equations of the plate and stiffeners were established by LW/SE and the governing equation of sandwich structure was written in narrow bandwidth form. FMST is adopted to establish the modal space of sandwich structure and the governing equations were converted into the final equations under fixed-interface modal. The equation of multi-layer sandwich structure was established under the fixed interface modal space. A series of numerical analyses were made and the results of FMST were good agreements compared with LW/SE. It is demonstrated that FMST was the accurate method.