PREDICTION OF MATRIX INDUCED DELAMINATIONS USING AN ENRICHED SHELL ELEMENT APPROACH

In order to achieve good predictability of the progressive failure of structural composite components, a proper modelling of the delamination process is crucial. Besides being a result of high interlaminar transverse (out-of-plane) stresses, delaminations are commonly initiated from stress concentrations at the tips of transverse matrix cracks, so called matrix crack induced delaminations (MCID) which is a challenging failure mechanism in laminated composites. In general, to capture delamination initiation and growth, detailed modelling of each ply by separate elements and interconnecting cohesive interface elements is required. However, due to restrictions on the simulation time, such high-fidelity models are not feasible in largescale industrial applications. Therefore, an adaptive enrichment methodology for the modelling of multiple and arbitrarily located delamination cracks using an equivalent single-layer (ESL) shell model has recently been presented. The methodology is based on an enriched shell element formulation , where arbitrarily many delamination cracks can be modelled using only one element through the thickness. The methodology has been shown to save substantial amounts of computational efforts, thus having the potential to enable computationally efficient simulations of progressive delamination failure in composite structures. Aiming to increase the industrial applicability of the proposed approach, we have now implemented the adaptive shell element in the commercial FE solver LS-DYNA. In addition, in order to extend the range of application, we have recently put specific focus on the modelling of MCID. In particular, we have investigated different methods to represent the transverse matrix cracks in an ESL framework and these methods have been compared with respect to their ability to capture the driving mechanism for delamination initiation. Comparisons have been made to the case where the matrix cracks and delaminations are explicitly modelled and to relevant experiments, e.g. the four-point bending test of a cross-ply laminate by Mortell et al