Dynamic Optimization Design Of Fiber Reinforced Composite Frame With Manufacturing Constraints

Nowadays,the lightweight design of structures is becoming more and more important in the aerospace and other engineering fields.The frame structure made of carbon fiber reinforced composite materials has been used in many structures due to its superior materials and structural properties.Based on the integrated multi-scale theory,this paper carried out the integrated multi-scale optimization design of the structure and material of the fiber-reinforced composite frame structure,with the first order frequency of the structure as the constraint and the structural weight as objective function.In the topology optimization design of composite frame structure under fundamental frequency constraints,when considering the cross-sectional area of the beam as the design variable,the feasible region of the optimization problem is composed of multiple unconnected subdomains.The global optimal solution of the topology optimization problem is usually located in the end point of the degenerate low-dimensional sub-domain.It is difficult to find the optimal solution with the optimization algorithm based on the gradient information.In this paper,the PLMP(PoLynomial Material interPolation)method for solving the dynamic singularity problem in isotropic material frame structures is introduced into the optimization of composite frames by deriving the equivalent stiffness of the composite pipe model.Considering the limitation of the traditional PLMP method,an improved PLMP optimization solution strategy is proposed,which can solve the difficulty in the traditional PLMP algorithm that the lower limit of the fundamental frequency constraint of the optimization problem is restricted by the value of the PLMP parameter.The improved PLMP optimization solution strategy increases the value range of the fundamental frequency constraint.A fiber-reinforced frame structure optimization model is established with the macroscopic area as the design variable,the fundamental frequency as the constraint and the structural weight as the objective function.Considering the fiber winding angle as the microscopic design variable,the commonly used [0°,45°,-45°,and 90°] in practical engineering are used for four alternative fiber winding angles.Taking into account the key manufacturing constraints in the fiber reinforced composite ply design,such as continuity constraints,10% constraints,balance constraints,damage tolerance constraints,symmetry constraints,etc.In the macro scale,adopting the improved PLMP solution strategy,the cross-sectional areas of the composite pipes are used as design variables.In the micro scale,the discrete composite material DMO(Discrete Material Optimization)method is adopted,and the discrete fiber winding angle is used as microscopic design variables to realize the lightweight design of the composite material frame under the constraint of the fundamental frequency.The optimization results show that the improved PLMP optimization solution strategy can effectively solve the singularity difficulties in the composite frame structure topology optimization under the fundamental frequency constraints.Compared with the traditional size optimization,the redundant pipes are deleted.The phenomenon of the instability in the optimization iteration process is eliminated.Achieve the topology optimization of the composite frame structure effectively.At the same time,the manufacturing process is considered in the macro optimization variables.The discrete cross-sectional area of the pipe is the macroscopic design variable.An integrated optimization model for fiber reinforced composite frame considering macroscopic and microscopic manufacturing constraints was established,with the fundamental frequency of the structure as the constraint,and the minimum structural weight as objective function.Different penalty strategies are applied in the optimization.The effects of different penalty parameters on the optimization result are compared.