A Study On Discrete Topology Optimization Of Fiber Reinforced Composite Structures

In recent years,with the increasingly stringent standards for energy conservation and emission reduction of automobiles,traditional metal materials have been unable to fully meet the design requirements of lightweight vehicles.From the body cover to the semi-structural parts,structural parts,high-performance composite materials in the automotive field is gradually wide and deep,and also brings a broader design space for the body structure design.For the composite pavement structure design,the choice of each ply material,the thickness of the ply,the connection method,etc.will have a great impact on the structural performance of the product.However,the existing main paving design method is still based on the steel structure design model,with reference to composite manufacturing and performance constraints.It does not give full play to the advantages of composite parts in the layer design,integrated molding and so on.The multi-phase discrete design is an optimized design method based on the different performance requirements of the specific structure of the part in the local area to obtain a more ideal anisotropic material distribution.Among them,the existing discrete design method adopts an idealized connection form between adjacent design sub-domains;and experiments show that the unreasonable distribution of the joints has a great impact on the mechanical properties of the joint region.At present,an interlaced splicing design structure is proposed,which attempts to solve the problem of stable connection between adjacent design sub-domains,and hopes to obtain relatively more reliable optimization design results.L-plate optimization design model and splicing joint stiffness test and simulation analysis respectively prove the proposed interlaced splicing layer structure has significant advantages in making full use of the different needs of the structural properties of the parts and effectively avoiding the negative impact of the unreasonable connection form on the overall performance of the part.In this paper,combined with commercial finite element analysis and optimization design software,a DMTO design system for discrete material and thickness topology optimization of splicing layup is established,which is beneficial to the promotion and further engineering application of the optimized design method.In the optimization design process,comprehensive consideration of the component performance design index,composite manufacturing constraints,joint area connection,integer programming variable convergence and other factors to optimize the design process,the optimized design results have good implementability.It effectively reduces the dependence of traditional topology optimization methods on engineering experience in the post-optimization process.The semi-analytic method is used to obtain the sensitivity information of the independent variables,and the gradient-based algorithm is used to improve the optimization calculation efficiency.Finally,taking the car back door model as an example,the accuracy of the optimized design model is verified by comparing the benchmark test with the simulation.In the DMTO design system,the RAMP and SIMP material interpolation models were used to optimize the calculations and the relatively ideal design schemes were obtained.The comparative analysis results show that the application of the layer optimization design system makes the target car back door assembly reduce the parts weight by 59.5% and 28.0% compared with the original steel structure model and the traditional composite layer design model,respectively.Based on the indicators,an ideal lightweight implementation effect has been achieved.