Research On Multi-scale Optimization Method For Structure Reliability Of Composite Material

The dispersibility of fiber reinforced composites is an important factor to restrict its further application.Utilizing the characteristics of composite materials,through reasonable design optimization and structural reliability improvement,it is of great significance to apply composite structure to more scenarios..At present,the analysis and design of the reliability of the composite structure mainly consider the macroscopic factors such as the layer angle and the layer thickness.Such structural reliability analysis lacks of the root causes of the dispersion of the composite material.Only considering the design of macro-parameters in improving the structure Reliability,did not consider the different layers of different fiber volume fraction of the situation,can not give full play to the advantages of composite materials.Therefore,based on the mesoscopic parameters,this paper predicts the performance of the macroscopic mechanical parameters of composites considering dispersion,and then establishes the reliability analysis model considering the mesoscopic and macroscopic parameters.Finally,the composite material structure is made to achieve synergetic multiscale parameters Optimize design.The following is the full text of the main research content:(1)The transfer relation between macroscopic mechanics parameters and mesoscopic parameters was established.By comprehensively investigating the mesoscopic parameters and dispersion data of composite materials,the statistical distributions of the mesoscopic parameters of the typical composite materials are given.By using the bridge model and the Monte Carlo method,the macroscopic performance prediction model,The transmission relation between the statistics of the macroscopic parameters and the parameters of the composite material was obtained,and the distribution of the results and the sensitivity analysis were done.(2)The structural reliability analysis model of the composite laminates with the mesoscopic parameters as variables was obtained.The stress-strain relationship of the meso-parameters of the laminates to loads is obtained by using the parameter transfer model of composite materials and the macroscopic mechanics theory.Based on the stress-strain relationship of the laminates,the layer-structure parameters Reliability analysis model of plywood structure,and verify the structural reliability index under different loads and different layers.(3)An optimal design model of the reliability of the laminated structure with multiscale parameters is established.Based on the basic principle of genetic algorithm,an optimal design model was established for laminates with fiber volume fraction and ply angle as independent variable,structural reliability index as constraint condition and minimum mass as objective function.The results of the optimization design show that the design of weight loss can indeed be achieved under the condition of ensuring the reliability with the consideration of macroscopic and mesoscopic parameters,and the influences of load conditions,load size and number of layers on the design of weight loss are analyzed.The results show that the optimal design of the multi-scale parameters is very obvious under the bending moment load.(4)Structural Optimization Design of Typical Type Aircraft Composite Landing Gear.Finite element analysis of the composite structure in the landing gear of the SR20 aircraft was carried out by using the finite element simulation software to obtain the loading conditions and stress cloud images of the landing gear composite structure when the aircraft landed.Based on this,The rib structure reliability analysis,get the structural reliability index.Under the condition of meeting the structural reliability index,the weight reduction design of the landing gear main frame and the front and back ribs is done with a coordinated multi-scale parameter.The results show that the optimal design method considering different fiber volume fraction and ply angle can obviously reduce the structural quality under the condition of ensuring reliability,and the validity of the multi-scale optimization method is verified.