Research On Mechanical And Electromagnetic Characteristics Of Composite Folded Core Sandwich Structure

In order to achieve the lightweight,exploring a new structure with light weight,low cost and high performance is one of the urgent problems to be solved in the aviation and aerospace industry.The folded core sandwich structure with high specific strength,high specific modulus and low Radar Cross Section has attracted lots of attention,and it is consider to be the most likely new sandwich materials used in Radar and Radome.In the present study,the new Ufolded core sandwich structure bases on the origami ideology are designed.Subsequently,the mechanical properties and electromagnetic characteristics were comprehensively analyzed and also compared with V-folded core sandwich structures.The main research contents are as follows:(1)The U-folded core sandwich structure was designed to increase the shear performance of V-folded core sandwich structure.A finite element simulation model by ABAQUS was established to compare the mechanic response between U-type and V-type folded core sandwich structures under compression and bending loads.Orthogonal test method was applied to optimize the geometric parameters of the folded core sandwich structure.Taking the specific strength as the target,geometrical parameters of the structure were determined.Subsequently,according to the theory of composite autoclave molding technology,carbon fiber was used to prepare the sandwich cores and epoxy resin was used to prepare panels.The U-folded core sandwich structures were prepared by autoclave process.(2)By compression performance test,the number of layers,braiding methods,shape of core and types of structure were compared.Compression force-displacement curve and deformation failure mode of sandwich structure were analyzed.Simultaneously,by finite element compression simulation,the defects including porosity,lamination,and cells deletion were researched.As the increasing of the proportion of defects,the mechanical properties decreases and different defects influence degree are different,the cells deletion is the largest.By impact experiments and simulation,the dynamic performance of the U-type folded core sandwich structure was explored.The impact test results show that the U-type folded core sandwich structure is local deformation under 100 J impact energy and both the panels and core are damaged.(3)V-type folded structure was combined with frequency selective surface technology to design and prepare the folded structure FSS sandwich plate.The FSS flexible screen was prepared by laser ablation,the sandwich plate was prepared by integrated molding.Subsequently,electromagnetic transmission characteristics of Y-type FSS unit and single station radar cross section characteristics of folded structure FSS sandwich plate were analyzed by HFSS finite element simulation software.The analysis results show that Y-type FSS unit has good band characteristics in the frequency band of 30 GHz～60GHz and resonant frequency is 38.5GHz.Simultaneously,the FSS folded structure sandwich plate has the characteristics of reduction of RCS.