Research On Ply Optimization Of Carbon Fiber Composites And Its Application In Maglev Car Body

Maglev vehicle,as a fast,comfortable and environment-friendly vehicle,has become one of the main trends in the future development of rail transit industry.Since maglev vehicle relies on electromagnetic force to support the body weight and the weight of passengers in the operation process,the lightweight design of maglev vehicle is of great significance.Carbon fiber composite materials are gradually used in the lightweight structure of maglev car bodies due to their excellent mechanical properties such as high specific modulus and high specific strength.However,the mechanical properties of the carbon fiber composite structure are closely related to its layering method,and its excellent mechanical properties can be fully utilized through the optimization of the layering.Therefore,this thesis will investigate the ply optimization of carbon fiber composites through material mechanical performance tests,numerical simulation methods,and genetic algorithms.Firstly,according to the requirements of the test standards for mechanical properties of fiber-reinforced composite materials,this thesis conducted the tensile,shear and compression mechanical performance tests on woven carbon fiber composite materials.Then,the basic mechanical property parameters,environmental coefficient and the force-displacement and stress-strain curves of the braided carbon fiber composites under different load forms were obtained through experiments.Secondly,the two-dimensional Hashin damage model and the fabric composite damage model were verified through experiments.It was found that the fabric composite damage model has higher simulation accuracy.Therefore,the effects of two simulation variables of the number of layers and the element type of the fabric composite material damage model on the simulation accuracy are studied.The result shows that as the number of layers in the interlayer bonding domain increases,the force-displacement curve and the stress-strain curve obtained by the simulation analysis are basically the same,but the calculation time increases sharply.The use of different element types has a little effect on the simulation analysis results.Then,based on the integrated concept of “design-analysis-optimization”,the cabin structure of a certain type of aluminum alloy magnetic levitation vehicle was designed by using woven carbon fiber composite materials,and a weight reduction of 43.9% was achieved.Meanwhile,high-precision numerical simulation method was used to make the static strength simulation analysis on the carbon fiber composite material compartment under the whole vehicle structure.According to the result,the stress of the bottom longitudinal beam is too large,so it is necessary to optimize the lay up of this part to reduce the stress.Finally,the finite element software was redeveloped through Python,and the parameterized simulation analysis of the carbon fiber composite structure was realized.Furthermore,based on genetic algorithm and parametric simulation analysis method,an ply optimization algorithm for carbon fiber composites was written.In addition,this algorithm was used to optimize the layering of the longitudinal beams of the bottom plate of the carbon fiber carriage.The maximum tensile stress after optimization is 440.9 MPa,which is 11.9%lower than that before optimization.