Structure Design Of The Composite Material ARM Of Large Hovercraft Duct

Considering the lightweight design of composite duct arm of the large-scale hovercraft,the structure of the arm is optimized in the following three aspects: configuration,material system and geometrical parameters.Based on those,a composite duct arm model is manufactured by vacuum introduction molding process(VIMP).After that,the mechanical properties of the arm are tested by designed testing system to verify the designed results.The problem of equivalent modeling and optimal design method for the main bearing structural members with complex load conditions and difficult to determine the interaction relationship with the rest of the structure is solved in this paper.First of all,the equivalent model of "cantilever plate beam" arm is established with large-end fixed,small-end edge translational.Constraints for the maximum bending deflection less than 6.22 mm,weight less than 120 kg,the optimization goal of the arm is to achieve the lightest weight.Second,the optimization configuration of the duct arm,the front and back edge reinforcement,the built-in stiffener,and the thickening structure from the small-end to the large-end,is confirmed through the topological optimization method.According to the structure,the material system is designed.Besides,based on the multi-island genetic algorithm,the optimized material system that the skin,before and after reinforcement,stiffeners are all carbon fiber and foam filling is obtained.At last,the pure carbon fiberfoam sandwich arm achieves the lightweight design with weight of 30.715 kg and the maximum bending deflection of 5.89mm。Finally,the scheme of composite fiber-foam sandwich is chosen to test and verify here.A full-size composite arm-like specimen is fabricated by VIMP,and the mechanical properties are tested.The error of displacement between the experimental value and the theoretical value is 26.88%,while the experimental value of the strain agrees well with the theoretical value.The experimental results show that the scheme and process are feasible for the optimization design of the composite sandwich structure with complex load conditions and difficult to determine the interaction relationship with the rest of the whole structure.