Study On Preparation And Mechanical Properties Of Aluminum Foam Sandwich

Aluminum foam sandwich (AFS) is a new type of composite materials, which is widely used in automobile manufacturing, aerospace, military defense and other fields. It has light, great energy absorption properties and sound insulation effect, and overcomes the low strength and poor corrosion resistance of aluminum foam. The better specific strength of AFS just meets the need of high security and low emission for automobile manufacturing. At present, aluminum foam sandwich has been successfully applied in design and manufacture of bumper and cover plate in Germany and other countries, but the domestic research in this field is still in its infancy.In this paper, the study on preparation of aluminum sandwich is carried in order to get the aluminum foam sandwich with high quality plate, uniform bubble holes and excellent mechanical properties. The quasi-static three-point bending and low speed dynamic impact testing on aluminum foam sandwich was carried out, and the deformation process and fracture mode of two kinds of AFS was studied providing reference to the architecture design and optimization of the aluminum foam sandwich applied to automobile. The valuable results obtained from this paper are as follows.(1).Foaming parameters and the pretreatment technology of titanium hydride have a great influence on the quality of aluminum foam sandwich during the preparation of aluminum foam sandwich, the appropriate technological parameters was summed up through a large number of experiments:foaming temperature is 710℃, foaming time is 2 minutes, cooling mode is air-cooled and water cooling, pretreatment temperature of titanium hydride is 500℃;(2).The growing process of bubble hole in the core layer is divided three phases: nucleation, growing and merging. The early phases of the foam, the growth of bubble hole is not obvious, bubble hole will grow in 1 minutes. The shape of the bubble hole in the early phases is elliptical, and round in the end;(3).Deformation process of AFS without middle layer after static three-point bending is divided three phases:elastic compression stage, platform stress stage, dense phase; deformation process of AFS with middle layer after static three-point bending is divided five phases:elastic compression stage, the first plastic platform stage, the first dense phase, the second plastic platform stage, the second dense phase. The yield strength and the length of platform stress zone of AFS with middle layer is better than those of AFS without middle layer, so the bending performance and energy absorption of AFS with middle layer is better;(4).There is no obvious difference between the two kinds of aluminum foam sandwich in the failure mode, the failure modes include panels bending, compaction damage, panel fracture, plastic hinge crack, core layer shear and so on. Bending performance and energy absorption performance improve with the increase of the density of the core layer, bending performance and energy absorption performance of AFS with the middle layer is superior to the one without the middle layer;(5).The deformation process of AFS in the low speed impact is divided five phases: elastic compression stage, platform stress stag, dense phase, complete failure stage. Two kinds of aluminum foam sandwich have the energy absorption properties, but the aluminum foam sandwich with the middle layer is better. The failure mode of aluminum foam sandwich after low speed impact includes four kinds:core layer shear, panels bending, panel fracture, core layer compaction, damage form is mainly associated with the internal defects of aluminum foam sandwich;(6).Impact velocity, core layer density and structure have main influence on impact properties, energy absorption and platform stress increase with the increase of impact velocity; with the increase of core layer density, energy absorption, yield strength, platform stress and fracture strength all increase; yield strength, platform stress and energy absorption of AFS with middle layer is better than those of AFS without middle layer.