The Modeling and Mechanical Analysis of Ribbed Grid Shell Structure with Advanced Composite

Author:Zhang Fu Sheng

Supervisor:xu jia zhong


Degree Year:2018





The advanced composite ribbed grid shell(RGS)is a new type of composite grid thin shell structure,which has the characteristics of overall load balancing and good robustness.The RGS not only has the advantages of high specific stiffness,high specific strength and strong structural design,such as the traditional composite grid structure(AGS),beam and cylinder,but also the simple periodic uniform isometric grid beam and plate structure to the non-cyclical inhomogeneous grid structure of space.The structure has been applied gradually in harsh environments such as aerospace,warships and military engineering.However,the design and mechanical analysis of the RGS exist the problems of the high order multidimensional,nonlinear buckling of the structure and the stiffness characteristics of the structural members in the service environment.Therefore,this paper presents the RGS shape representation model and mechanical analysis method of space Gauss geodesic for its structure.Low dimensional 3D RGS geometric model and finite element analysis model are established based on Riemann space mapping.Taking the typical spatial non periodic heterogeneous grid structure(radome)as an example,the validity of the above models and analysis methods is verified.Moreover,the mechanical properties of the structure under actual service environment are analyzed and explored.There are high order multidimensional problems in the characterization model of the spatial structure of composite components.The method of space geodesic differential mapping is applied to realize the form representation of components.Based on the curvature properties of Riemann space structure,the geometric shape equidistance of the curved surface structure of the spatial component is mapped to a unit sphere by using the principle of the Gauss differential fundamental and the shortest path of the geodesic path.A 2D geodesic differential RGS structure mathematical model of the warp and weft ribs is established on the sphere of the unit to reduce the dimension of the structural representation of components.The differential equation of the arc length and arc angle of the geodesic differential RGS is established by using the basic configuration of the Gauss I and II of the geodesic differential equation to realize the reduction of the structural characterization of the component.Taking the structure of a ship borne spherical cap radome as an example.The geodesic RGS structure model of the radome has been built.Low order low dimensional modeling of RGS structure of composite spherical cap radome based on two vector angles and bandwidth of unit sagittal projection.The characterization of the parameters of isometric,non-equidistant and bandwidth isoparametric variables and the shape of the model is studied,which lays the foundation for the study of the mechanical properties of the following structure.In view of that nonlinear buckle problem of the rib ribs of RGS structure after the stress on the structure of RGS structure,the mechanical response law of the RGS structure under the given load is investigated by establish a finite element mechanical analysis model of RGS structure by using single cell node as vector mode and superimposing them.By means of mechanical analysis and simulation experiments,the nonlinear deformation response law of each isoform heterogeneous antenna cover model transmitted from pole to periphery along each rib braid is compared and analyzed in vertical loading with different thicknesses,different knitting angles and different widths.In addition,the load-displacement response characteristics of different braided structures to the RGS structure of the antenna cover under the same load are studied.The shipboard radome RGS structure specimens are prepared by premiered carbon fiber reinforced composite material belt(CFRP)based on manual laying and vacuum hot pressing technology.The effectiveness of the RGS structure modeling and mechanical performance analysis method is verified through the experimental study of actual ballast of the specimen.Through the above experiments and data analysis,the data analysis shows that the maximum stress of the RGS structure increases with the increase of the compression displacement,and increases with the increase of the knitting angle,and the maximum deformation decreases with the increase of the knitting angle.This accumulates effective experimental data and design experience for mechanical design and optimization of RGS structures based on different materials.In order to further study the service performance of the radome RGS structure,a numerical wind tunnel simulation experiment of the radome RGS structure has been done for the external load of the radome in the actual service environment.Based on the foregoing theoretical and experimental research,the finite element numerical wind tunnel method is adopted.The surface uniform thickness skin of the above RGS model is shaped into a sphere crown radar radome with the adoption of numerical wind tunnel method.The wind force is applied to cover the wind with different wind directions and different wind angles.The stress and deformation of the RGS structure of the radome and the mechanical laws under the maximum limit wind speed are studied.The mechanical influence of wind load on different braided structure covers is compared,and the mechanical buckling characteristics of the advanced composite RGS structure under dynamic load are studied.It provides design check and theoretical reference for solid composite radome design of RGS composite structure.In summary,the design idea of progressive integration is achieved through component RGS spatial structure characterization modeling,finite element mechanics analysis model establishment and experimental verification.The theoretical and experimental results of this study can provide new ideas for the light weight and innovative design of polymer component structure,and for integrated light weight design of polymer RGS component with higher specific stiffness and carrying efficiency.It can also provide basic methods and reference for the realization of light weight forming and mechanical study on polymer grid and shell structure components.