Delamination initiation and propagation modelling with an enriched shell element formulation

For achieving good predictability of the deformation of structural composite components in crash simulations, a proper modelling of the delamination process is crucial. However, due to industrial restrictions on the simulation time of crash simulations, detailed modelling of each ply by separate elements through the thickness is not feasible. A potential remedy is to adopt the concept of adaptive shell elements which can be enriched whenever delaminations need to be accounted for. Hence, a structural model of a thinwalled laminate can thereby initially be built up from a single layer of shell elements through the thickness. During loading, the model is then enriched locally in critical areas where delamination is predicted. In this con- tribution, we show the potential of such an approach, where delamination cracks are adaptively introduced in the analysis based on a stress criterion in terms of the transverse stresses. A specific challenge is that these stresses are predicted with low accuracy in the FE model, whereby a post-processing step is proposed where an improved prediction is reconstructed based on the momentum balance equations. We show the potential of the proposed methodologys ability to capture initiating and propagating delaminations, and can conclude that the proposed methodology appears to be suitable for the simulation of thin-walled structures undergoing substantial delaminations