Experimental Investigation On Repeated Low Velocity Impact Damage And Residual Compressive Strength Of Honeycomb Sandwich Panel

Honeycomb sandwich panel has high specific strength and high specific stiffness,widely used in various engineering fields.During the service of the honeycomb panel,it is often subjected to different types of impacts,such as the impact of seawater while the ship is traveling,and the impact of a wrench falling when servicing equipment.The impact event causes a significant reduction in the residual strength of the honeycomb panel.Foreign and domestic scholars have done more investigations on single impact honeycomb panel,but fewer investigations on repeated impact honeycomb panel.This thesis takes honeycomb sandwich panel as the research object,and studies its repeated low velocity impact,quasi-static indentation and residual compressive strength.The main contents are as follows:Experimental investigation on repeated low velocity impacts of honeycomb sandwich panel.An impact tester was used to conduct different energy and different frequency impact tests on the same area of the honeycomb panel.The damage after repeated low velocity impacts and mechanical response of impact process were analyzed.Experiments show that as the impact energy increases in the single impact,the impact damage also increases.When the honeycomb panel is not penetrated,the maximum contact force increases as the impact energy increases.Among repeated impacts,the load stiffness of the honeycomb panel in the first impact is the smallest.When the total impact energy is the same in repeated impacts,the smaller the number of impacts,the greater the damage of the honeycomb panel.In single and repeated impacts,the honeycomb panels show good energy absorption effect.Simulation of repeated low velocity impacts of honeycomb sandwich panel.Repeated impacts were simulated using ABAQUS simulation software.Simulation results show that the simulation results are better when the front panel of the honeycomb panel has no fracture damage,and the simulation results are quite different from the experimental values when the honeycomb panel has large fracture damage.Experimental investigation on quasi-static indentation of honeycomb sandwich panel.The pit depth after impact was used as the damage parameter,and the honeycomb panel was loaded using quasi-static indentation method to manufacture honeycomb panel with the same pit depth.The damages of both impact and quasi-static at the same pit depth were compared.The mechanical response during quasi-static indentation was analyzed,and simulation was performed for quasi-static indentation.Digital image correlation method was used to observe the change of strain and displacement of the bottom surface.Experiments show that the damage of the honeycomb panel caused by quasi-static indentation is greater than the damage caused by impact at the same pit depth.The energy absorbed when the honeycomb panel is damaged in the quasi-static indentation is less than the energy absorbed when the honeycomb panel is damaged in the impact.The simulation results agree well with the experimental results.The strain of the convex of the honeycomb panel is mainly tensile strain.In the same time interval,the displacement increase of the honeycomb panel convex is smaller than the displacement increase of the indenter drop.Comparison of residual strength of impact and quasi-static indentation.Through the residual strength experiment,the average residual strength of the honeycomb panel at the same pit depth was compared.The digital image correlation method was used to observe the strain in the pit and convex of the honeycomb panel during compression.Experiments show that since the damage of quasi-static indentation is greater than that of impact at the same pit depth,the average residual strength of quasi-static indentation is less than that of impact at the same pit depth.The strain change in the compression direction of the pit increases with the increase of the force,and the larger the convex,the more obvious the strain change at the convex.