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A computational framework for simulation of dynamic delamination in composite blades and wings

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Novel blade designs of improved airfoil cross sections and wings feature continuous shape morphing. This allows such flexible structures to adapt continuously their shapes with a strong potential to increase the lift capability and the aerodynamic stability. Some new wind turbines are considered with passive blades shape adaptation without control devices. The simplicity of this passive pitching control system makes it a low-cost addition to the rotor and could dramatically increase the energy conversion. The operation of passive flexible blades in various conditions make them prone to several mechanical failure modes that should be controlled. One of the challenging concerns is to control the delamination between rigid inner part and flexible external part of the blade. This delamination may take place through several dynamic loading scenarios. The mechanical degradations associated with the shape morphing operations of the blade are not completely addressed yet. Delamination in composite laminates has been the subject of extensive research both at structural and material levels. However, the study of interfacial crack evolution in response to stress waves in a laminated structure is still a topic of active investigation form both modelling and experimental perspectives. In the proposed research work, we aim to develop a computational framework to predict the delamination under stress wave propagation. This deals with different modes of material degradation due to serviceability state loads. As for ultimate limit state loading the proposed models should possess the predictive capability of detecting damage and failure locations and corresponding traction forces accurately. Dynamic fracture analyses are envisaged with a model of bi-material laminate including two layers: one as a rigid part and another as a flexible elastic material. Due to the singularities of stress and strain fields at the crack tip, instead of using stress-based failure criteria, J-integral and G-values are applied for the study of mixed-mode fracture. Numerical approaches involve eXtended Finite Element XFEM, Cohesive Zone Model CZM and Continuous Damage Model CDM to analyse both inter-ply and intra-ply fracture in laminated layers.