Optimization Design Of Variable Stiffness Composite Structures Based On Meta-models

Due to their excellent mechanical properties,fiber laminated composites have been widely used in aerospace,deep-sea,and other military and civil engineering fields.To take advantage of its high stiffness-to-weight and lightweight features,it is crucial to study its designability.The traditional linear fiber laminated composites have limited the designability of the composite structures.In order to fully explore the potential of structural designability,it is necessary to study the variable angle fiber laminated composite material to improve the mechanical properties of structures.In this paper,the finite element model of the variable angle fiber laminated composite cylinder is established using the finite element analysis software Ansys.The optimization design of variable stiffness cylinder under single load(with or without ovality)and combined loading conditions is considered:(1)Considering different geometrical defects or specific shape manufacturing(ovality)under pure bending moment load or axial compressive load respectively,with the fiber path as design variables,the buckling failure as constraint,and the maximum anti-buckling as the objective;(2)Under the condition of coupled bending-torsion load,with the fiber path is taken as design variable,the buckling failure and strength failure as constraints,and the maximum bending capacityas the objective.The calculation burden of the optimization design problem is huge due to the finite element analysis and its iteration in the optimization.In order to improve the computational efficiency,the Kriging meta-model is utilized to fit the structural response,and the genetic algorithm(GA)is adopted to optimize the structure.In the construction of Kriging meta-model,a mixed update method is proposed to reduce the number of evaluations of finite element analysis.The results show that under the condition of pure bending at both ends of the cylinder structure,the optimized variable stiffness(VS)structure is better than the commonly used quasi-isotropic(QI)laminated structure,and the anti-buckling capacity is increased by 23.9%.Compared with the cylinder structure designed by QI,VS design can largely compensate for the loss of anti-buckling resistance caused by ovality.Under combined conditions,VS design can improve the anti-buckling resistance of the structure to some extent in comparison to QI design.The optimization design of variable stiffness composite enlarges the design space,and makes the strength and stiffness of the structure more reasonable,leading to the uniform distribution of internal force in the structure.