Research On Mechanical Properties Of High Temperature Alloy Honeycomb Panels Used In Thermal Protection System

Metallic thermal protection system plays an important role in protecting the aircraft from overheating,and the outermost layer of it is usually made up of high temperature alloy honeycomb panels,which have the advantages of light weight,high specific strength,good heat resistance performance and so on.Because the complex load changes during the working process of aircraft,the honeycomb panels should have better load properties to guarantee the stable work of metallic thermal protection system.Therefore,it is quite meaningful to study the out-of-plane properties of honeycomb panels under different load conditions.Firstly,the nickel-based high temperature alloy was selected as the base material to produce the corrugated board without obvious defects,which by the way of gear rolling and sizing.On the basis of research of optimal resistance spot welding parameters for thin foils,the corrugated boards are connected as the honeycomb core through resistance spot welding technology.After the cutting,flat grinding and cleaning process of the core,it was joined with the panels which are made of the same material by vacuum brazing technology.Secondly,the quasi-static compression test and the dynamic impact test using the split hopkinson pressure bar were carried on the honeycomb panels.The deformation process and yield stress of honeycomb panels are analyzed and compared under the two different out-of-plane loads.It was found that the deformation process and the change trends of stress-strain curve are similar.In the dynamic impact tests,the strain rate and yield stress increase with the increment of bullet velocity,which indicates that the honeycomb panels is the rate dependent structure.That may be caused by the rate dependent property of material and the special cylindrical structure of honeycomb panels.Finally,the quasi-static compressive and dynamic impact properties are studied by the finite element method in ANSYS/LS-DYNA.In the compression,the stress concentrated in the middle of core walls and then expand outside,but in the dynamic process,the stress increases in all parts of the core and then concentrated in the middle of core walls.In the numerical simulation of compression,the compressive yield stress of honeycomb panels obviously increases with the increment of wall thickness,but with the increment of wall height,it increases first and then decreases.Besides,the wall thickness has a bigger effect than wall height on the change of compressive yield stress.