Numerical Modelling and Experimental Study of Sandwich Shells with Metal Foam Cores

摘要

The trends in automobile industry always include the use of new materials such as those needed for the passive safety of vehicles and they are one of the most important strategies to reduce injury of passengers during traffic accidents. Associated with the development of security systems, there is the possibility of improving efficiency by the introduction of materials that lead to weight reduction, having a direct impact on fuel consumption and lower carbon emissions. The present work aims to study the behaviour of sandwich structures, composed by a foam core with two outer layers of metal sheet (all structure being aluminium). The study of the composite structure behaviour, its mechanical characterization and numerical modelling is essential to analyse the mechanical performance of structures based on this type of materials. This step is fundamental in preliminary design, since the different materials of the composite structure show different mechanical responses. The differences in mechanical behaviour are demonstrated by the axisymmetric compressive stress states tests and also by the influence of hydrostatic pressure in the yield of the aluminium foam porous material [1], while the yield of the homogeneous solid material (aluminium sheet) can be considered as pressure insensitive. In order to correctly characterize separately these two materials of the composite (outer layers and core), a set of tests were performed. The characterization of the aluminium sheet was performed in a series of tensile tests, using three different rolling directions. For the metal foam core characterization a series of uniaxial compression tests were performed [2]. The experimentally obtained results were applied in the development of numerical models for this kind of sandwich structure. The models include elastoplastic constitutive relation, where a distinct plastic domain for different materials is accounted for, as well as, the influence of hydrostatic pressure in the yield of the porous material. Also, the validation of the elastoplastic models is performed by comparing results obtained by numerical simulations with those obtained experimentally.