Analysis And Optimization Of Laminated Composite Shells With Variable Stiffness

Different from the traditional straight fiber laminate structure,the tow angle-changing laminated structure is a kind of variable stiffness composite material,in which the angle of the laying fiber is continuously changed and traverses the trajectory along the specific trajectory to realize the fiber laying.The fiber angle can be continuously changed on the same layer,thus the design flexibility of the composite material can be expanded,and the direction characteristic of the fiber can be fully utilized to make it possible to improve the structural performance and reduce the structural weight.In this paper,the development of laminated composite structures with variable rigidity is described,and the current research situation at home and abroad is described.Based on the study of predecessors,the mechanical properties of composite laminates are studied.The main works are as follows:The translation method and the parallel method are introduced to analyze the reasons why the gaps or overlapping regions are likely to occur.The advantages and disadvantages of the two methods are compared and the translation method is selected.The basic theory of the laminated plate(shell)and the method of sequence response surface modeling are introduced.The quadratic function is chosen to generate the response surface,and the optimal solution of the original problem is obtained by genetic algorithm.Designing of fiber curve locus of variable stiffness laminates,the finite element model of the variable stiffness laminates was established by the idea of continuous curve fiber discretization.The buckling of the variable stiffness laminates was analyzed influence of fiber trajectory parameters and geometrical parameters on buckling under axial and bi-axial compress loads.The effects of fiber trajectories and geometrical parameters on the frequency of the laminates were discussed.The flexural and frequency characteristics of the variable stiffness laminates were optimized by the sequence response method.The T0 and T1 optimal solutions were obtained.The fiber placement path and stacking sequence scheme of the variable stiffness cylindrical shell and the elliptic cylindrical shell are given,and their finite element models are established in ANSYS.Under different external loads,with the critical buckling coefficient as the target,the critical trajectory parameters are optimized,and the influence of the cylindrical shell geometry on the buckling performance was alsoanalyzed.The results show that under the load of bending moment,using the curve of fiber layer θ instead of [45/0/-45/90/-45/0/45/90]s laminated shell contains 45 degree line layer,the buckling performance of the cylindrical shell is improved remarkably.By controlling the continuous change of the tow angle,the rigidity of the elliptic cylindrical shell is changed in the circumferential direction to reach the proper increase of the stiffness of the flat part,and the stiffness of the part with small radius of curvature is reduced appropriately,which can improve the buckling performance of the elliptic cylindrical shell.