Experimental Study And Simulation On Mechanical Behavior Of Density Gradient Aluminium Foam Sandwich Structures

Aluminium foam is a kind of porous material which is made of aluminium or aluminum alloy and treated by foaming process.The unique hole structure makes the aluminum foam material with excellent properties such as cushioning,energy absorption,sound insulation and noise reduction,which has good prospects for application in the fields of aerospace,shipping and transport packaging.Density gradient aluminum foam sandwich panels have a large potential in terms of blast impact resistance,but a systematic theory about mechanical behaviours have not yet been developed and further research is needed.Therefore,this paper investigated the mechanical behaviour of density gradient aluminium foam(DGAF)and its sandwich structure(DGAFS)through a combination of experimental and numerical simulations,with the aim of revealing the mechanical properties,deformation processes,failure modes and energy absorption mechanisms of DGAF and its sandwich structure.The main research were as follows:The quasi-static mechanical properties of DGAF were investigated by quasi-static tests.The stress-strain curves of DGAF were obtained,and the influence of the density gradient distribution on the quasi-static compression mechanical behaviour of DGAF was investigated in relation to its deformation process and failure mode,It was concluded that the deformation of DGAF has a clear direction:from low density to high density expansion,Besides,the negative density gradient aluminium foam has the best energy absorption,while the plastic platform of DGAF had multiple platform areas due to the inconsistent density distribution of layers.The quasi-static mechanical behaviour of DGAFS was investigated by quasi-static threepoint bending tests,and the effects of density gradient distribution and face-sheet thickness on the quasi-static three-point bending mechanical behaviour of DGAFS were analysed.The results showed that DGAFS overcome the plastic platform discontinuity of DGAF.The positive density gradient aluminium foam sandwich structures had the best comprehensive mechanical performance.The greater the panel thickness,the greater the load-bearing capacity,the more complex deformation and failure modes of DGAFS.The aluminium foam can fully played the role of cushioning and energy absorption when the face-sheet thickness is 1.2 mm in this study.Numerical simulations were used to investigate the dynamic compression mechanical behaviour of DGAF.The deformation process and the effect of density gradient distribution on the dynamic mechanical behavior of DGAF under dynamic impact were analyzed through the force-time curve and velocity-time curve.The deformation of DGAF under dynamic compression loads had a clear direction:from low density layer to high density layer.In addition,the density gradient aluminium foam had better impact resistance than the equal density gradient aluminium foam,and the low-density aluminium foam played an important role in cushioning energy absorption.A finite element simulation study of the intrusion process of DGAFS was carried out and the deformation process and damage mode of DGAFS under impact loading were analysed.The effects of initial impact velocity and face-sheet thickness on the impact resistance of DGAFS were analyzed.It was found that there was a significant strain rate effect in DGAFS under dynamic loading.Besides,at higher initial impact velocities,the middle core layer,lower core layer and lower panel played a major role in cushioning and energy absorption.In addition,the DGAFS relied more on the upper panel to resist external shocks.