Preparation And Mechanical Properties Of New Composite Metal Foam Core Sandwich Panels

The composite metal foam core sandwich panels has excellent properties such as light weight,high specific stiffness,high specific strength,and impact resistance.It has been widely used in aerospace,rail transit,weapons and equipment and other fields.At present,the method of gluing is mainly used at home and abroad to prepare composite metal foam core sandwich panels,but the bonding method has problems such as easy to oxidize and crack of the junction at high temperature.There is also the problem of low connection strength due to the large number of holes on the surface of the foam metal sandwich layer.The upper and lower layers of the composite metal foam core sandwich panels usually use a single homogeneous material,so it cannot meet the requirements of both strength and toughness.Therefore,the preparation of composite metal foam core sandwich panels layer,the selection and preparation of upper and lower panel layers,and the exploration of combined methods and processes are of great significance.In this project,a new composite metal foam core sandwich panels was prepared by vacuum hot pressing sintering technology using 316L stainless steel hollow spheres/aluminum matrix composite as composite metal foam core sandwich panels layer and Ti/Al₃Ti layered composite material as panel layer.In the experiment,316L stainless steel hollow spheres/aluminum matrix composites were prepared by the method of first aluminum liquid casting and heat preservation,and Ti/Al₃Ti layered composites were prepared by summarizing the process.On the basis of the successful preparation of composite metal foam core sandwich panels layer and panel layer materials,a new composite metal foam core sandwich panels was compounded after the exploration of vacuum hot pressing sintering process.The microstructure of a variety of composite materials prepared in the experiment was characterized by optical microscope,scanning electron microscope,energy dispersive spectrometer,X-ray diffraction technology.The mechanical properties of various composite materials prepared by hardness,quasi-static compression and dynamic compression tests were also studied.Finally,the ballistic performance test of the prepared composite was carried out,and the failure behavior of the material was verified by combining finite element simulation.A 316L stainless steel hollow spheres/aluminum matrix composite material was prepared by the method of first aluminum liquid casting and then heat preservation.Moreover,the preparation process is optimized to solve the problem of holes in the surface when it is used as a sandwich layer.Then,the microstructure of the composite material under different holding times was observed,and it was found that with the extension of the holding time,a transition layer was formed between the hollow sphere and the matrix,and the transition layer was analyzed and judged to be Al_0.5Fe₃Si_0.7 phase.Ti/Al₃Ti layered composites with flat surface and no macro pores were prepared by summarizing the process.The preparation of a new composite metal foam core sandwich panels by vacuum hot pressing sintering was explored,and the best preparation effect was concluded at a pressure of 550°C+0.5MPa.Through microscopic observation,it was found that a transition layer was formed at the junction of the sandwich layer and the panel layer,and the analysis determines that the transition layer is Al₃Ti phase.The microhardness test of the new composite metal foam core sandwich panels before and after hot pressing sintering was carried out,and it was found that the microhardness of the Al matrix of the sandwich layer was significantly improved,and the microhardness of other materials did not change significantly.The quasi-static compressive properties of a variety of prepared composites were tested.The yield strength of 316L stainless steel hollow spheres/aluminum matrix composite is 117.2±6.6 MPa and the energy absorption is 55.9±4.2J/mm³;The yield strength of the new composite metal foam core sandwich panels prepared by gluing was 134.6±5.7 MPa and the energy absorption was 57.6±3.4 J/mm³.The hot press sintering preparation reached 162.6±7.1 MPa,and the energy absorption was 76.6±5.2 J/mm³.Compared with 316L stainless steel hollow spheres/aluminum matrix composite material and gluing,the new composite metal foam core sandwich panels prepared by gluing has been greatly improved.Moreover,it was observed that the 316L stainless steel hollow spheres/aluminum matrix composite material and the glued new metal sandwich structure had a main crack fracture at an angle of 45°.The new composite metal foam core sandwich panels of hot pressing sintering produces multiple main cracks during the compression process,and finally the material forms a“drum”type fracture in the vertical direction.A variety of composite materials prepared in the experiment were tested for ballistic impact.It was observed that the impact test of 316L stainless steel hollow spheres/aluminum matrix composite showed a“tunnel effect”and did not exert a good energy absorption effect of porous metal materials.The finite element simulation also verifies the“tunnel effect”generated by the hollow sphere composite during the penetration process.The damage behavior of Ti/Al₃Ti layered composite material in impact test is as follows:disbonding of the upper TC4 layer,crushing of the Al₃Ti layer,and“petal-like”failure on the back of the target material.The impact test results of the new composite metal foam core sandwich panels are as follows:a small range of disbonding between the upper Ti/Al₃Ti layered composite material and the sandwich layer,the bending deformation of the sandwich layer,the“fracture cone”of the sandwich layer,and the“petal-like”failure of the back of the target material.The same destructive behavior is observed through finite element simulation,which proved the effectiveness of finite element simulation.