Structural Optimization Design Of Composite Materials With Variable Stiffness Based On Principal Stress Method

With the wide application of composite materials in various fields,the research on the mechanical properties of composite materials has been gradually deepened.Automatic wire laying technology and automatic spread with the development of technology make the fiber can realize Angle laying,and compared with the conventional laminated plates,the variable stiffness composite laminated plate design degrees of freedom is high,the fiber path can be adjusted according to the actual load demand curve,increase or reduce the local stiffness,implementation to avoid stress concentration,so has the very good application prospect.The increase of design variables makes the relationship between curvilinear fiber path and the mechanical response of variable stiffness composite laminates more complex.In this paper,the influence of curvilinear fiber path on the mechanical properties of variable stiffness composite laminates is studied and discussed,and the optimization of curvilinear fiber path and variable stiffness composite laminates is mainly studied.As for the optimization method of curve fiber path,the principal stress method has high design degree,while the function method has simple definition and easy implementation,which can ensure the continuity of fiber.Considering the above factors,this paper proposes to use the contour line of smooth surface to realize the continuous fiber Angle.For the square plate under compression and shear load,the fiber Angle of the curve was optimized based on the principal stress method,and then the integral algorithm of 3d surface reconstruction was used to obtain3 d data points,and the fiber path of the curve was described and optimized using the quasiuniform B-spline surface.The optimization results show that this method not only ensures the continuity of the curve fiber,but also obtains better mechanical properties of the curve fiber path,and discusses the effects of aspect ratio and mesh size on the curve fiber path optimization.Considering the actual manufacturing constraints,the curvature of the fiber needs to be constrained in the optimization process.For the optimal design of variable stiffness laminates,the optimal design of variable stiffness laminates based on function method and principal stress method is carried out respectively.For the variable stiffness laminates based on function method,linear change function and cubic polynomial function are used to describe and optimize the fiber paths.For the laminates with variable stiffness based on the principal stress method,based on the optimized fiber path,the Angle corresponding to the center of each element is rotated ±45° and90° respectively,and the layering sequence of the laminates is optimized by genetic algorithm.Through a square plate example,the constant stiffness laminates,the variable stiffness laminates based on function method and principal stress method are compared.The results show that the variable stiffness laminates have better mechanical properties under strength constraints,and the optimization effect of the variable stiffness laminates based on principal stress method is better.