Abstract: The experiment had designed six pieces of aluminum-foam-sandwich panels, including three sandwich panels without sides and three sandwich panels with sides, with the materials of side panel and faceplate of the thickness of aluminum-foam cores of 40mm, 60mm and 90mm, respectively. The bending resistance experiment had been carried out on the sandwich panels. The load-displacement (P-δ) curves as well as the process of deformation and failure were being made. Based on the formula of Gibson peak bearing capacity, the failure mode diagram of a sandwich panel without sides was founded. The formula of the peak bearing capacity of a sandwich panel with side was deduced and the failure mode diagram was built up. The results are as follows: the thicker the aluminum-foam core is, the higher the bearing capacity will be, contributing to higher load stiffness. The built failure mode diagram could predict the mode of sandwich panels. Compared to sandwich panels without sides, the bearing capacity and load stiffness can be significantly improved only by adding sides, constraining the further changing after aluminum foam cracked. Generally speaking, each failure mode of a sandwich panel without sides just solely matches one piece of a failure mode diagram, while the failure mode diagram of a sandwich panel with sides is divided into four regions where the face yield independently corresponds two regions.