HE static and fatigue damage predictions of composite structures with the presence of stress concentrators are still a challenging task due to the existence of an inherent gap of a continuum damage mechanics and fracture mechanics based modeling approach. The presence of stress concentrations resulting from either the fabrication induced defects or the presence of geometric discontinuities can render the predictions of damage initiation mesh sensitive within a finite element solution framework. While an energy driven failure criterion can be included in the static damage prediction to alleviate the mesh dependence, its extension to fatigue damage initiation and propagation is not straight forward since the fatigue damage progression is controlled by the crack growth driving force along its front ie Paris law, without invoking an energy dissipation principle. A conventional SN based fatigue damage initiation is applicable for composite components without the presence of stress singularity. Both the cohesive1-4 and virtual crack closure technique5-8 (VCCT) have been used to perform fatigue damage evaluation of composite structures. The application of the cohesive model has shown its benefit when simulating the damage initiation followed by its propagation without using an initial flaw. However, an explicit crack front is not defined in the cohesive model. In addition, due to the continuum damage description of the cohesive model, an explicit implementation of the fracture mechanics based Paris law cannot be easily accomplished. With predefined surfaces, the strain energy release rate can accurately be computed using a VCCT approach with the knowledge of the crack location or propagation path driven by the self-similar crack growth requirement. An implicit crack front representation based on the extended finite element approach is developed to alleviate the mesh dependence7, 8. Given the distinct nature of the modeling approach for static and failure prediction, a unified approach based on a dual spring model is developed for a delamination crack growth prediction. The initiation of a delamination crack under either a static or a peak load prior to the application of fatigue cycles is characterized by a cohesive material model of a user-defined spring element for Abaqus where the damage initiation is driven by the energy dissipation. For a given initial crack under fatigue loading, a distribution of linear penalty springs is used along a pre-defined crack path and the resulting fatigue crack driving force is computed from a VCCT based method by extracting the spring force ahead of the crack front and crack opening displacement behind the front. A Paris law type fatigue growth law with its mode mixity is applied for fatigue crack growth prediction. The developed dual spring element is verified first using benchmark examples developed by Kruger and Carvalho9-13, including Double Cantilever Beam (DCB), End-Notched Flexure (ENF) and Mix-Mode Bending (MMB). The dual spring elements coupled with a continuum damage modeling approach are used next to explore its applicability for the static and fatigue damage prediction of NASA/Boeing sub-elements with the migration of a matrix crack. The effects of mesh sensitivity and a transversely matrix crack parameter on the crack path and crack growth rate behavior are explored during the blind and recalibrated analyses. Unlike the NASA/Boeing specimen, the applicability of the developed modeling strategy is explored for UTC sub-elements with the presence of multiple ply drop areas. Multiple delamination cracks are simulated at the ply drop locations. While a continuum damage approach is applied for …