Impact analysis of laminated and sandwich composites using a plate finite element with strain energy updating

This paper deals with finite element simulation of low velocity-low energy impacts on sandwich composites with laminated faces. A refined zig-zag model with a high-order piecewise representation of in-plane and transverse displacement components is used as a structural model in order to accurately simulate the effects of the transverse normal stress and strain. The goal is to develop a tool for improving the accuracy of conventional plate models, so as to enable the impact analysis of sandwich composites. A strain energy updating process is used for this purpose. As is customary, the Hertzian law and the Newmark implicit time integration scheme are used. The contact radius is computed within each load step by an iterative algorithm, which forces the impacted top surface to conform, in the least-squares sense, to the shape of the impactor. Then, the failure analysis is performed and the material properties of the failed areas reduced. Nonlinear strains of von Karman type are used because the transverse displacement can be quite large even when the plate deflection is small. Comparison with numerical and experimental results published in literature show the present model to be able to accurately predict the impact force and the damage it induces.