| The sandwich structures with metallic foam core have been widely used in civil engineering and other engineering fields owing to their light weight,high specific stiffness and excellent energy absorption.There are two different forms of metallic core,namely homogeneous foam core and gradient foam core.Compared with homogeneous foam core,the gradient foam core has more strongly variability and designability,which has attracted more and more scholars attention.Due to complicated geometric structures of gradient foam core,it is difficult and significantly to establish the theoretical models for mechanical behavior of sandwich structures under local loading.For the local indentation behavior of gradient foam metal sandwich structures,the theoretical models are established,and then the mechanical properties and design parameters are studied.The main contents and conclusions are as follows:(1)The theoretical model of the indentation behavior of sandwich beams with gradient foam core was established,and the reliability of the theoretical model is verified through numerical simulation results used ABAQUS code.The influences of the gradient foam cores on the localized behaviour of the sandwich beams are discussed when the mass of the gradient foam cores is kept constant.T he results show that the deformation capacity of the negative gradient beam increases as the gradient difference increases.(2)The theoretical model of the indentation behavior of sandwich panel with gradient foam core is established.And a gradient influence function is defined which is proposed to describe the effects of gradient change of foam cores on local deformational behavior of sandwich panels,which is composed of the core layer material parameters,geometric parameters,and gradient change parameters.The analytic solutions for the plastic deformation profile of upper face sheet and the indentation force of spherical indenter are obtained,which are validated using the existing theoretical model and finite element code ABAQUS?.Subsequently,the influences of the gradient change on indentation response and energy absorption of sandwich panels with gradient metallic foam core are also investigated.The results show that when the gradient difference is kept constant,the mechanical properties of the sandwich panel with negative gradient foam core are better than the sandwich panel with positive gradient foam core.(3)The theoretical model of the indentation behavior of sandwich panel with gradient foam core considering thickness variation is established.When the mass of core is kept,the influences of the core layer thickness variation on the maximum plastic deformation zone,the indentation force and energy absorption of energy absorption are discussed.The results show that the mechanical properties of the sandwich panel with negative foam core in three areas will increase with thickness increasing of the core layer.The reliability of theoretical model was verified by numerical simulation.(4)The theoretical model of the indentation behavior of sandwich panel with dual gradient foam core is established.The influences of the dual gradient foam cores on the localized behaviour of the sandwich beams are discussed.The results show that changing the geometric parameters of the dual gradient foam core can improve the deformation ability and energy absorption of the sandwich panel.The reliability of the theoretical model through the ABAQUS simulation verification. |
