Damage Propagation in composite structures using an embedded global-local Approach

Since most composite materials are characterised by brittle failure, with low margin of safety through ductility, the failure mechanisms in composites must be investigated and suitable prediction analysis tools need to be developed. In many structural applications a three-dimensional progressive damage approach, able to take into account all the physical phenomena characterising the damage on-set and propagation until the final failure, needs to be adopted. In the present paper a three-dimensional progressive damage approach for laminated composites will be presented. This approach is based on the use of a progressive damage finite element with the geometrically non-linear finite element formulation for stress calculation. The FEM element has been integrated with Hashin’s failure criteria to split fibre and matrix failure modes and with the ply discount method to simulate the stiffness degradation in each ply. The FEM tool was tested together with an embedded global-local approach in order to prove its effectiveness when dealing with complex structures that need to be modelled by using different mesh densities and different element types. As an application, the structural behaviour of a notched panel under tensile load has been investigated and the obtained numerical results have been compared with numerical and experimental data from literature. Finally, a comparison between a full 3D model and a global-local model has been performed in order to evaluate the effectiveness of the developed progressive damage approach in global-local analyses.