Analysis of the Effectiveness of Different Finite Element Modelization for the simmulation of Composite Plates Behaviour in Presence of Delaminations: An Essential Step Towards a Fully Damage Tolerant Design Approach

With the aim to develop a damage tolerant design approach, a numerical tool for the prediction of the mechanical behaviour of a composite laminated structure in presence of an embedded delamination, which could grow under the application of a certain load level, has been developed and validated within the Task 2.3 of the CESAR project. Fracture mechanics concepts have been adopted and used in conjunction with the finite element method to characterise the delamination status: Energy Release Rate distributions at the delamination front have been computed by using the Modified Virtual Crack Closure technique and a linear growth criterion has been adopted to establish critical conditions which lead to the delamination propagation. As the effectiveness of the energy based approach proposed strongly dependends on the accuracy of the computation of forces and displacements at nodes on the delamination front, two delamination modelizations have been proposed and their results compared in terms of Energy Release Rate distributions. The modelization more suitable to simulate the growth phenomenon has been selected and used to analyze the mechanical behaviour of a composite plate with an embedded circular delamination starting from the local buckling of the debonded area up to the global-buckling of the panel taking into account the delamination growth phenomenon. The results obtained have been validated against numerical and experimental data taken from literature.