| As one typical porous material,honeycomb was widely used in the design of anti-corrosion structure of buildings,transportation and aerospace since it is capable in maintaining the stability of the plateau crush stress in a relatively wide range and exhibits a good energy absorption capacity.However,when adopted individually,honeycomb material generally presents some problems such as low load-bearing capacity and limited energy dissipation in the crashing process.As one protective component,large volume is required to meet the energy dissipation under strong impact in practical applications,which limits the application of honeycomb materials in the defence field.Therefore,the formation of lightweight-filled composite structures by the method of filling lightweight materials into honeycomb structures to enhance the crashworthiness of honeycomb materials and improve the spatial utilization and the bearing capacity of structures is gradually favored by most researchers.Due to the diversity of microstructure of honeycomb skeleton and filledmaterial,the filled honeycomb structures has strong designability.In this study,the crushing performance of random honeycomb and lightweight material-filled honeycomb structures,the influence of mesostructure parameters on the mechanical properties of the structure and the interaction mechanism between the honeycomb skeleton and the filled-material subjected to quasi-static and impact loadings was experimentally and numerically investigated,so as to provide guidance for the design of the filling honeycomb composite structures for crashworthiness.The main research contents and results of this paper are as follows,(1)Based on the two-dimensional random Voronoi structure,a three-dimensional random honeycomb structure was constructed by unit shrinkage settlement and radial stretching,and the corresponding geometric model was compiled into STL file for 3D printing.In order to meet the different mesostructure accuracy requirements of random honeycomb structures,nylon 12(PA 12)and polylactic acid(PLA)random honeycomb structures were prepared by multi-jet fusion(MJF)and fused-deposition(FDM)3D printing technology in this study.(2)The foam concrete-filled PA 12 random honeycomb structure was constructed,and the quasi-static in-plane crushing tests were conducted on the unfilled random honeycomb structures and filled random honeycomb structures.The effects of cell irregularity,relative density and cell size of the honeycomb structure on the in-plane crushing performance of unfilled PA 12 random honeycomb structures and filled random honeycomb structures were analyzed.The results showed that the deformation mode of unfilled PA 12 random honeycomb structure was dominated by cell irregularity and cell size,and showed the deformation characteristics of brittle failure.The deformation mode of foam concrete-filled PA 12 random honeycomb structure was dominated by the mesostructure parameters of the honeycomb skeleton.Due to the interaction between foam concrete and honeycomb skeleton,the energy absorption of the structure was enhanced.By controlling the microstructure parameters of the honeycomb skeleton,the interaction between the honeycomb skeleton and the foam concrete during the in-plane crushing of the filled-structure was influenced,thus affecting the macroscopic mechanical properties of the structure.(3)Quasi-static in-plane crushing tests were conducted on the unfilled PLA random honeycomb structure and polyurethane foam-filled random honeycomb structure.The effects of cell irregularity,relative density and density gradient of the honeycomb structure on in-plane crushing performance of unfilled PLA random honeycomb and polyurethane foam-filled random honeycomb structures were analyzed.The results showed that the deformation modes of PLA random honeycomb structures and polyurethane foam-filled PLA random honeycomb structures were dominated by the cell irregularity and density gradient.Filling polyurethane foam improved the toughness and bearing capacity of the structure.The mesostructure characteristics of honeycomb skeleton and filling mode determine the macroscopic mechanical properties of polyurethane foam-filled structure by influencing the interaction between polyurethane foam and honeycomb skeleton.(4)Mesoscopic finite element models of gradient random honeycomb structure and foam concrete-filled structure were established,and the dynamic crushing performance of the structure under constant-velocity impact loading was studied.The results showed that the deformation mode of unfilled gradient random honeycomb structure and foam concrete-filled composite structure was dominated by the density gradient of honeycomb skeleton and the impact velocity.With the increase of impact velocity,the inertial effect was gradually enhanced,and the energy absorption capacity of unfilled negative gradient random honeycomb structure was improved.The energy absorption of the foam-concrete filled gradient random honeycomb structure was less dependent on the density gradient of honeycomb skeleton under low velocity impact.The energy absorption of the foam-concrete filled uniform and positive gradient random honeycomb structure was better under medium velocity impact.The energy absorption of the foam concrete-filled negative gradient random honeycomb structure was the best under high velocity impact.(5)Under mass impact,the influence of density gradient on the crushing performance of filled random honeycomb structure was further studied.Under the high-speed impact of mass,the foam concrete-filled gradient honeycomb structure converted most of the impact kinetic energy into the plastic dissipation energy of the specimen,and the honeycomb skeleton was the main energy absorption component.The negative gradient honeycomb filled with foam concrete exhibited good energy absorption performance and large maximum crushing displacement under high-speed impact of mass.When the mass was impacted at medium velocity,the maximum crushing displacement of foam concrete filled with positive gradient random honeycomb structure was larger at the end of mass impact.When the mass was impacted at low-speed,the maximum crushing displacement of the filled-structure was not sensitive to the density gradient. |
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