Study On Compression Behavior And Numerical Simulation Of Fly Ash Cenosphere/Polyurethane Aluminum Alloy Syntactic Foam

Aluminum foam has been widely used as a new functional and structural material in recent years.Its unique porous structure determines its low density,high porosity and large specific surface area.These characteristics make it has sound insulation noise reduction,buffering energy absorption and other functions,is widely used in aerospace,national defense,military,automotive protection and other fields.Therefore,it is of great significance to study the mechanical properties and deformation behavior of aluminum foam.With the development of material research,a novel composite was fabricated by mixing polymer into aluminum,which was called interpenetrating phases composite(IPC),and the viscoelasticity of polymer is used to improve the mechanical properties of foam materials.With the development of materials,it has become an important means to improve the energy absorption efficiency of foam materials to use the foam filled with polymeric containing hollow particles.Based on the study of the mechanical properties of aluminum foam,the energy absorption effect and mechanical properties of composite aluminum foam were studied,according to the experimental data,the numerical simulation of aluminum foam is carried out,and the feasibility of the numerical simulation is analyzed.Therefore,the specific content of this paper is as follows:(1)Experimental study on quasi-static and dynamic compression of spherical cell aluminum foam with homogeneous pore morphology and size has been conducted.Deformation mechanisms of aluminum foam in the quasi-static compression at both macroscopic and mesoscopic levels was identified by using digital image correlation method.Results show that compressive strength,plateau stress and energy absorption are significantly improved by increasing loading strain rate,that is,spherical cell aluminum foam exhibits obvious strain rate sensitivity.Because of the inhomogeneous cell wall thickness and the random distribution of cell wall defects,deformation bands dominate compressive behavior during the compression process of aluminum foam,and the strain concentration zones also appear on the single cell hole at the cell wall defects.Implications of compressive behaviors operating on mesoscopic cell walls and formation of macroscopic deformation bands have been discussed.Deformation modes of cells are mainly divided into three types:axial compression,shear,torsion and shear combined deformation.The failure mode of cell walls at the whole deformation zone is mostly determined by shear deformation,which is apparently dependent on cell wall thickness and the loading direction.(2)The aluminum matrix syntactic foam was fabricated by pressure infiltration technique,the filling material is a syntactic foam material with fly ash cenosphere as the main component and polyurethane foam as the binder.Dynamic compressive and quasi-static tests were carried out to examine the compressive response of syntactic foam in this paper.Results show that,the compressive stress-strain curve of syntactic aluminum foam is the same as that of other metallic foam materials,which include three typical processes:elastic stage,stress plateau stage and densification stage.The syntactic foam has higher compressive strength and energy absorption than aluminum foams.Under quasi-static compression,the energy absorbed per unit volume increases by 85%when the compacted strain is reached.When the size of cenosphere is constant,with the density varying from 1.0g/cm~3 to 1.33g/cm~3,the compressive stress and the energy absorption performance increased with the density.The dynamic mechanical behavior of aluminum matrix syntactic foam was investigated by Split Hopkinson pressure bar(SHPB)system in this paper.Both kinds of aluminum matrix syntactic foam have strain rate effect.The syntactic foam has higher compressive strength and energy absorption under dynamic loading,however,due to the different sizes of cenospheres,the dynamic compression results of two kinds of syntactic foam are different,and the energy absorption effect of small size under dynamic impact is the best.(3)An experiential constitutive model of composite aluminum foam was established and compared with the experimental results.The finite element model of cell pore arrangement and porosity similar to that of real aluminum foam was established by the finite element analysis software LS-DYNA,and its feasibility was confirmed.The above research combined the numerical simulation with the experimental results,comprehensively analyzed the mechanical properties and energy absorption effect of the new composite aluminum foam,which is of great significance for the selection of buffering energy absorption materials and experimental methods.