Experimental Study On The Compression And Tnesile Mechanical Behaviors Of Aluminum Foam/Polyurethane Composites

As a new engineering material that combines structure and function,aluminum foam has many excellent properties.In recent years,with the gradual deepening of its mechanical properties research,its application range is also expanding.In order to improve the mechanical properties of aluminum foam and stimulate its application potential in the field of civil engineering vibration reduction,this paper processes spherical open-cell aluminum foam/polyurethane composite material(Spherical Open-cell Aluminum Foam/Polyurethane,SPAF/PU composite material for short),based on the concept of interpenetrating phase composites(IPC materials).A series of experimental studies and numerical simulations have been carried out around the compression and tensile mechanical properties of SPAF/PU composites.The main research contents and main conclusions of the thesis are as follows:(1)The compressive mechanical properties of SPAF/PU composites under monotonic compression,cyclic compression at different amplitudes and cyclic compression at specific amplitudes were carried out with different temperature conditions.The monotonic compression deformation mechanism and cyclic compression deformation mechanism and energy dissipation principle of composite materials were discussed.The effects of temperature on the monotonic and cyclic compression mechanical properties of composites were analyzed.The results show that the filling of polyurethane not only improves the uniaxial compressive strength of aluminum foam,enhances the plastic deformation ability of the composites,but also compensates for the defects of insufficient resilience of foamed aluminum,and greatly improves the energy-dissipating capacity of aluminum foam under cyclic loading.In addition,temperature has a great influence on the compression mechanical properties of SPAF/PU composites.Under the small strain amplitude,the yield strength of the composite increases with the increase of temperature,the deformation recovery ability is enhanced,and the energydissipating capacity is improved.Under the large strain amplitude,with the increase of temperature,the damage degree of the composite material is aggravated,the bearing capacity is gradually decreased,and the energy consumption capacity and deformation recovery ability are also weakened.(2)Based on monotonic compressive mechanical properties test of SPAF/PU Composites,a macroscopic uniaxial compression constitutive model of SPAF/PU composites considering temperature effect was established based on the Liu-Subhash model,which provides an effective way to predict the uniaxial compression mechanical properties of SPAF/PU.Based on the characteristics of cyclic compressive stress-strain curves of SPAF/PU composites under different amplitudes,a piecewise nonlinear model is proposed to fit the cyclic loading and unloading stress-strain curves of composites which can reflect the cyclic compression mechanical properties of composites at different temperatures perfectly.(3)Quasi-static tensile tests of foamed aluminum materials and SPAF/PU composites with different porosity were carried out.The effects of porosity on the tensile mechanical properties of the two materials were analyzed.Combined with the tensile deformation process of aluminum foam and composite materials,the deformation mechanism and failure mechanism of the two materials were discussed.The results show that the tensile stress-strain curve of aluminum foam is composed of linear elastic deformation section,plastic deformation section and fracture failure section,and has typical nonlinear characteristics.The tensile stress-strain curve of SPAF/PU composites is similar to that of foamed aluminum,but the filling of polyurethane effectively compensates for the effects of initial defects in the aluminum foam sample,making the deformation of the composite more uniform.Compared to the aluminum foam material,the plastic deformation ability of the composite material is increased by 40%,and the tensile strength is increased by 7%.The failure of foam aluminum and SPAF/PU composites under tensile load is semi-brittle failure,which is a sudden damage caused by the defects of the cell edges after certain plastic deformation of the cells.Secondly,the experimental results show that the porosity has a great influence on the tensile mechanical properties of aluminum foam and composite materials: the elastic modulus,tensile strength and elongation at break of the two materials increase with the decrease of porosity.Among them,the elongation at break of composites is most affected by porosity.Finally,using the macroscopic phenomenological model of foam material,the monotonic tensile stress-strain curves of aluminum foam and SPAF/PU composites were fitted to establish macroscopic uniaxial tensile constitutive model of foamed aluminum and SPAF/PU composites considering the influence of porosity.These provide an effective way to predict the quasi-static tensile mechanical properties of aluminum foam and its composites.