Experimental Study On Quasi-static Mechanical Properties Of Closed-cell Aluminum Foam And Its Sandwich Beams Under Multi-temperatures

Aluminum foams are widely used in the automotive transportation,aerospace,ship transportation and other fields because of their high specific strength,high specific stiffness and high energy absorption rate,etc.However,the aluminum foams fail to meet the requirements of strength and stiffness when used independently,and they are usually necessary to combine with the conventional dense metal materials to form sandwich structures.At present,the researches on the mechanical properties of aluminum foams and their sandwich structures are mainly concentrated at room temperature conditions.With the increasing potential of aluminum foams applications and the development of science and technology,the requirement for ambient temperature in the aerospace field is becoming increasingly demanding.It needs to explore the mechanical properties of aluminum foams at extreme temperatures such as high and low temperatures.Based on experimental research,this paper studies the mechanical properties of closed-cell aluminum foams and their sandwich beams at different temperatures with theoretical analysis.The main work and research results are as follows:(1)The stress-strain curves of aluminum foams at different temperatures are obtained through the quasi-static compression test.It is found that the closed-cell aluminum foams under high temperature conditions have obvious temperature softening and have a slight hardening at low temperature.In the quasi-static compression test,the yield stress,the platform stress and the energy absorption of the aluminum foam decrease and the plastic platform section becomes longer with the increase of the temperature;however,the compaction strain does not change with the different temperature on the whole.Analysis of the energy absorption characteristics of aluminum foams and the energy absorption efficiency diagram as well as the ideal energy absorption efficiency diagram indicate that aluminum foams are an ideal energy-absorbing materials and closer to the ideal energy-absorbing materials in high temperature conditions.(2)The quasi-static three-point bending deformation of sandwich beams at different temperatures was studied by means of theoretical analysis and experiment.It is found that the bearing capacity of sandwich beams which adhesive with high temperature glue is lower in the three-point bending test under the room and low temperature.The earlier emergence of panel degumming leads to the decrease of carrying capacity and energy absorption,so it is not conducive to structural safety protection.The ultimate bearing capacity and the energy of the absorption increase and the displacement where ultimate bearing capacity occurs decreases with the increase of the thickness of the core.However,the ultimate bearing capacity and the energy absorption decrease with the increase of the loading span.Under low temperature conditions,the ultimate bearing capacity and energy absorption are slightly higher than those under the normal temperature,showing the phenomenon of aluminum foam hardening,while under high temperature conditions,the ultimate bearing capacity and energy absorption are much smaller than those under the normal temperature,additionally,the ultimate bearing capacity and energy absorption decrease with the increase of temperature,showing the phenomenon of aluminum foam softening.