This thesis investigates the effect of local debonding on the residual fatigue life of a sandwich composite consisting of CFRP face sheets and an aluminum honeycomb core. Local debonding alters the load-transfer mechanism between the face sheets and the core and leads to increased stress concentrations in the vicinity of the damage boundary, which may promote further damage propagation under cyclic loading. The analysis was carried out using the finite element method implemented in Abaqus. Numerical models with circular and square debonded regions of different sizes were considered. A representative shear stress was determined from the numerically obtained S$_{12}$ and S$_{13}$ stress components, while the residual fatigue life was estimated using two Wöhler curves. The results showed that increasing damage size leads to higher representative shear stresses and a corresponding reduction in the predicted fatigue life. For comparable damage dimensions, square-shaped debonds produced slightly higher stress levels than circular debonds. The comparison of the two Wöhler curves further demonstrated that the predicted residual fatigue life is highly sensitive to the input data used in the fatigue assessment.
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