Size effects in metallic foam core sandwich beams

Foams exhibit size effects: if the specimen dimensions are of the same order as the cell size, the moduli and strength depend on specimen size. Metallic foams have particularly large cells (typically 2–20 mm), potentially giving rise to size effects when they are used in sandwich beams. Previous studies have shown that the shear strength of metallic foams bonded to rigid plates increases by over 50% if the specimen thickness is equal to the cell size. In this study, sandwich beams with aluminum alloy faces and aluminum alloy foam cores were tested in three-point bending to characterize the effect of the beam depth on the limit load. Beams of constant ratio of core thickness to span length but different absolute values of core thickness were tested, and the measured limit loads were compared to analytical values. The analysis gives a good description of the measured limit load when the shear size effect is accounted for.