Bilateral Filter For The Fiber Angle Optimization Of Variable Stiffness Composite Structures

With the continuous improvement of modern science and technology,the advanced manufacturing technology of Fiber Reinforced Composites(FRC)structures is booming,represented by Automated Tape Laying(ATL)and Automated Fiber Placement(AFP)technology,which makes the Variable Stiffness Composite(VSC)structure in which the fibers are laid along the curve become possible.Compared with the constant stiffness composite structure in which the fibers are laid along a straight line,it provides better designability,so it has received widespread attention.However,the curved fiber placement puts forward a number of manufacturing constraints on the fiber layout that must be met,and when these constraints are not met,problems such as difficulty in manufacturing or structural defects can occur.Therefore,how to design a manufacturable Variable Stiffness Composite structure has become an important issue.In response to this problem,this thesis integrates the bilateral filter into the continuous fiber angle optimization method and the Shepard-interpolation-based composite structure optimization method.Taking the structural compliance as the objective function,a mathematical model for the optimal design of single-layer variable stiffness composite structural fiber angles is constructed,and the bilateral filter is used to filter the sensitivity of design variables,and the manufacturability problem of fiber placement is solved in the optimization process.In the optimization design,the bilateral filter defines a circular filtering area for each design point.In this area,the sensitivity of design variables is filtered by the bilateral filtering,namely domain filtering and range filtering,to smooth the sensitivity of design points.The filtered sensitivity is used to update the corresponding design variables.Numerical examples show that the manufacturability of fiber placement can be improved by the bilateral filtering.By using the continuous fiber angle optimization method and the Shepardinterpolation-based composite structure optimization method integrated with bilateral filter,a large number of numerical examples are used to compare the objective function value in the optimization results,the parallelism,and the curvature of the fiber placement path.It is found that the bilateral filtering parameters have a significant impact on the optimization results.Furthermore,the influence rules are summarized and the reasonable range of bilateral filtering parameters is determined.