Buckling Analysis And Optimization Of Composite Laminate Plates Under Complex Loads With Free Edges

With Composite materials are widely used in various fields with its excellent performance,and the most typical one is a fiber reinforced resin matrix composite laminated plate.Its structural mechanical properties are influenced by various factors such as the material parameters of the the material parameters of single layer plate,the lay-up angle of the laminated plate,and the stacking sequence,which make it more difficult to study and apply it.Therefore,it is possible to obtain the desired optimal performance by accurately analyzing the mechanical properties of composite laminated plates and designing the laying angles and layering sequence.Accordingly,the Generalized Differential Quadrature(GDQ)method was used to analyze the buckling of laminates under complex loads with free edges,and the stacking sequence optimization for maximizing buckling loads combining the Adaptive Direct Search Simulated Annealing(ADSA)algorithm.The main contents include:Firstly,based on the GDQ method,the equations of the buckling differential equation and the boundary conditions with free edge are discreted.Then the non-dimensional critical buckling load coefficients of the laminate plates are programmed by MATLAB software.In order to solve the problem of oscillating and difficult convergence of composite laminate plates under to complex loads with free edges,shear loads,and inplane linear changes,the GDQ method adopts a grid point parameter perturbation strategy with free corners.The new grid point discrete method is adopted at the point.The combination of the grid point parameter perturbation strategy and the novel lattice point discrete method greatly improves the computational stability of the GDQ method in solving the buckling behavior of laminate plates.By comparing the results of the Finite Element Method,Levy method,and Extended Kantorovich Method,the effectiveness of the perturbation strategy and the high efficiency and accuracy of the GDQ method are verified.At the same time,the application of GDQ method in the structure of the plate and shell is also extended.Secondly,the buckling behavior of symmetric composite laminate plates under different boundary conditions,load conditions,and aspect ratios are analyzed using the perturbed GDQ method.The effects of their symmetry on the buckling behavior of laminate plates were discussed in detail.Finally,based on the perturbation GDQ method,the non-dimensional critical buckling load coefficients of the composite laminate plates is obtained,and the ADSA optimization algorithm is used to optimize the buckling behavior of composite laminate plates with the lay-up angle as the design variable.The optimization results show that the laminated square plates whose optimal stacking sequence are complementary angles,have the same buckling behavior with symmetrical loads and symmetrical boundary conditions;the shear load has the greatest influence on the buckling behavior of laminate plates,and the smaller shear load can improve the buckling behavior of laminate plates when the free edge is subjected to axial load,but the shear load will reduce the buckling behavior of laminated plates when the free edge is not axially loaded;The buckling behavior of the laminate plates can be increased by increasing the linear change rate and modulus ratio of the load;The number of plies larger than 8 have little effect on the buckling behavior of the laminate plates.