Abstract: Deformation and damage mechanisms of sandwich and multilayer beams composed of aluminum foam core and metallic face sheets under four-point bending condition are investigated by in-situ surface displacement analysis software (SDA). Plastic collapse of the sandwich beams within the foam core is by two basic modes：One is indentation (ID), which is resulted from concentrated deformation on the beam beneath the loading rollers; The other is core shear (CS) that is con-trolled by maximum shear stress on the center of beam. Beams tend to fail in ID mode when FID, the loading limit of the in-dentation, is less than FCS, the loading limit of the core shear. Conversely, CS mode takes places. This criterion, however, can not be used directly to judge failure mode of the multilayer beams. Mixed failure ID + CS mode takes place when face sheets of multilayer beams displayed similar ID characteristic in sandwich beams. Face sheets that do not display ID characteris-tic in sandwich lead to failure in multilayer beams in pure CS mode.

Key words: Aluminum foam, Core shear Four-point bending, Indentation, Sandwich and multilayer beams