Study On Design And Fiber Placement Process Of Variable Angle Composite Laminates Of CF/PEEK

Carbon fiber composite materials are widely used in the aerospace field due to the advantages of excellent specific stiffness and specific strength.The automatic placement technology can take full advantage of the anisotropy of the composite material,guiding the tows to steer within a certain curvature range to produce a variable-angle composite material component.Compared with the traditional straight fiber structure,it has a more flexible design space in terms of load-bearing stability,vibration resistance and light weight.However,the method of curved fibers will introduce more design variables,making the composite material structure design and automated fiber placement process more complicated.In order to promote the practical application of variable-angle components in the aerospace field,the design,optimization and manufacturing process of curved fiber laminates are studied with the purpose of improving the first-order buckling load and the first-order modal frequency of the laminates.Based on the six fiber reference paths of straight line,linearly-varying fiber angle curve,arc curve,sine curve,bezier curve and cubic polynomial curve,the relationship between the path position,fiber angle,and curve curvature and the design parameters is derived.The variable-angle laminate is constructed based on the translation mode of the tows completely overlapped,and the expression methods of the variable-angle laminates are given.Based on the mapping relationship between the reference path variables and the laminate structure,a functional module for variable-angle laminate finite element modeling and mechanical performance analysis was written.Through the secondary development of Abaqus/Python,a variable-angle laminate design optimization platform is built that integrates finite element modeling,mechanical performance analysis,structural design optimization,and automatic placement trajectory planning.In order to improve the optimization efficiency and search capabilities of genetic algorithms and multi-objective genetic algorithms,the fitness call and initial population generation modules are customized,and finite element analysis is used to calculate the fitness of the laminate.Based on different reference paths,and considering the fiber curvature,the optimization problems of increasing the first-order buckling load,increasing the first-order frequency,and simultaneously increasing the first-order frequency and the first-order buckling load are respectively explored.And a series of structural optimization schemes for laminates and open-hole laminates are obtained.Based on the variable-angle placement process,a seven-segment placement path is proposed,and the automatic planning module of the variable-angle placement track is compiled in combination with the working logic of the automatic placement equipment.The process parameters such as hot air gun temperature,mold temperature,placement speed and placement pressure were optimized by uniform experiment method.Laminates are fabricated according to the optimal placement process parameters.And vibration modal tests and compression buckling experiments are carried out to prove that the firstorder frequency and first-order buckling load of the optimized laminates are improved,which proves the effectiveness of the optimization algorithm for laminate structure.