Stacking Sequence Optimization Research Of Variable Stiffness Composite Laminates Including Manufacturing Constraints

Lightweight of automobile is an important trend to alleviate the increasingly severe energy shortage and air pollution. Because of the superiority in material property, composite has got wide attention in lightweight of automobile and has been applied in automobile such as carbody. The continuous fiber reinforced composite with variable stiffness design is strongly designable and hence the degree of lightweight of automobile can be markedly improved through optimizing the laminates to fully exploit the advantage of material. Since the optimization method for variable stiffness design can hardly take manufacturing constraint into account, the manufacturability of optimization result is unsatisfactory and the optimization method can not attain industrial relevance. Several methods for improving manufacturability of optimization result were proposed in this paper and a mathematical model of minimum structural compliance was established based on multiphase topology optimization theory. A sensitivity analysis was carried out under different methods and a software platform was built for the research. Thus this paper isof important theoretical significance for engineering application of variable stiffness optimization method.Based on mathematical morphology, a topology density filter was established for the aim of improving manufacturability of thickness distribution in each ply. Compared with other filters, the filter was more capable of overcoming the adverse effect of numerical instability on manufacturability of optimization result. Meanwhile, the ability of the filter to control the minimum size of structure and hole based on machining accuracy was another advantage of the filter in improving manufacturability of optimization result. The distinct and continuous thickness distribution in optimization resultsverifies the effectiveness of the filter.The manufacturability of ply angle distribution in each ply was enhanced via creating an improved material interpolation method and a material selection variable filter. The material interpolation method couldincreasingly penalizeintermediate material selection variable by introducing penalty function and consequently uncertainty of ply angle was eliminated distinctly. Based on property of material selection variableand vector filtering methods in color image processing, the fuzzy vector filter was chosen to filter material selection variable. The numerical examples demonstrate that the filter could ensure continuity of ply angle distribution in each ply and manufacturable size of ply region according to machining accuracy.A parameterization method of laminates thickness distribution was proposed and made it possible for multiphase topology optimization method to optimize laminates thickness distribution. The density distribution function was able to ensure continuity of material distribution along the ply thickness direction and consequently eliminate the intermediate void which can be found in other methods.The application scope of multiphase topology optimization method was extended from composite lamina to laminates by this parameterization method. Meanwhile, the parameterization method could reduce the number of design variables and constraints and also integrate other methods proposed in this paper. The numerical examples verify the compatibility of methods proposed in this paper and demonstrate that optimization result can satisfy multiple manufacturing constraints simultaneously with high efficiency.