| Aluminum foam has excellent properties such as energy absorption,thermal insulation and sound insulation because of its unique pore structure,so aluminum foam is widely used in traffic,aerospace and protection engineering.However,a large number of pores in aluminum foam also lead to its poor anti-penetration ability,and debris spatter is easy to be caused by high-speed impact.Polyurea elastomer has the advantages of light weight and low price,convenient construction and good physical and chemical properties,which can ease the impact,reduce the oscillation and reduce the stress amplitude.Therefore,the combination of the two can further improve the protective performance of aluminum foam.Therefore,this paper takes the composite structure of aluminum foam with different density and polyurea foam with different polyurea coating methods as the research object to carry out the following studies:(1)Uniaxial compression test was conducted on aluminum foam specimens with three densities of 0.35g/cm~3,0.55 g/cm~3 and 0.75g/cm~3 respectively.The results show that the stress-strain curves of aluminum foam with different density are wired elastic stage,plastic yield stage and densification stage.With the increase of the density of aluminum foam,the platform stress increases significantly,and the compressive mechanical properties of aluminum foam are positively correlated with the density.(2)Polyurea and aluminum foam substrate are made into polyurea-foam aluminum composite structure by spraying technology.through dynamic impact test,it is found that coating polyurea can reduce the stress concentration on the impact surface of bullet,so as to improve the protective performance of aluminum foam.And because of the good viscoelasticity of polyurea itself,it can prevent the debris spatter of aluminum foam after impact to a great extent,and greatly reduce the secondary damage to the human body and structure.Compared with the three polyurea coating methods,the protective effect of double-sided polyurea coating is the best.(3)Based on the study of the closed-cell aluminum foam structure of spherical cells used in the experiment,through reasonable simplification,the three-dimensional model algorithm of aluminum foam was compiled by using Python,and the three-dimensional model of random spherical cellular aluminum foam with adjustable pore size,porosity and cell size was generated.According to the calculation results of the finite element model with different cell size at the same density,the compressive mechanical properties of aluminum foam have no obvious cell size sensitivity.Through the analysis of the total energy absorption,energy absorption efficiency and ideal energy absorption efficiency of aluminum foam,it is known that the total energy absorption efficiency of aluminum foam increases with the increase of density,but the energy absorption efficiency and ideal energy absorption efficiency of0.35g/cm~3 foam are relatively the best.Through the analysis of the load-time history curve and energy absorption of the composite structure with different thickness of polyurea elastomer coating,it is found that the impact resistance of the composite structure is positively correlated with the increase of coating thickness in the range of 2-6mm.It can provide some reference for further research of aluminum foam follow-up test and numerical simulation. |
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