Research On Matching Of Local Impact Face-sheet And Core Of Honeycomb Sandwich Structure And Strengthening Of Resistance

Under the background of lightweight,impact safety protection of equipment is an important challenge to develop advanced rail transit system.As a kind of composite structure with the advantages of light weight,good technological economy and excellent comprehensive mechanical properties,honeycomb sandwich has become the preferred scheme of lightweight train body structure.With the continuous improvement of train speed and mileage,the car body is facing the potential threat of foreign body impact such as ballasta,hail,birds and so on.The new car body structure should have better resistance to local impact while satisfying the lightweight.Therefore,this thesis focuses on the local impact behavior,energy absorption mechanism and strengthening mechanism of honeycomb sandwich.The main research contents are as follows:(1)Based on the theoretical model of front face-sheet displacement field,the indentation response model of honeycomb sandwich structure under quasi-static impact was constructed,and the critical value of flexure/penetration under different structural parameters was calculated according to the yield and failure theory of face-sheet and shell structure.The three-element coupling regulation mechanism of impact radius,panel strength and core strength on response mode was studied.Two evaluation indexes,indentation depth and penetration level,were introduced to evaluate the local impact resistance of sandwich structure,and the law between structural parameter,response mode and local impact resistance was obtained.The dimensionless parameters of face-sheet/core matching coefficient are further simplified into a binary regulation of impact radii and face-sheet/core matching coefficient.On this basis,some suggestions on the design of sandwich structure parameters under different impact conditions and application scenarios are given.(2)The impact response of sandwich structure with different honeycomb array forms is studied.Based on the theory of face-sheet and shell with finite displacement,the energy dissipation mechanism of common surface core material in buckling stage was analyzed.The effects of different array forms on deformation modes and local impact resistance of sandwich structures are compared.The local impedance of sandwich structure was improved by functional gradient design.(3)Hierarchical enhancement research was carried out for in-plane honeycomb.The design of cell wall hierarchical replacement was introduced into Kagome cells,and the analytical model of plateau stress of the hierarchical structure was constructed based on two-scale analysis method.Parametric analysis was carried out to further reveal its strengthening mechanism.(4)Study on the impact resistance enhancement of hierarchical reinforced honeycomb sandwich structure for typical foreign body hit parts of high-speed train body.The replacement scheme of honeycomb sandwich structure with hierarchical enhanced configuration was designed,and the static strength was checked,and the anti-local impact performance was studied.It was proved that the design scheme had better deformation resistance and energy absorption effect under the premise of satisfying the lightweight.