An analytical, numerical and experimental study of the failure behaviour of composite T-joints under pull-off loading is presented, including the investigation of using of carbon nanotubes in the design to increase damage tolerance and failure resistance. The paper purposes the use of nanocomposites at local hot spots in the structure that are susceptible to delamination as an alternative to traditional methods used to suppress delamination. A multiscale approach is adopted to determine the mechanical properties of the nanocomposite. These effective properties are then used to analyze the structural response of a T section stringer using detailed finite element models. The stringer is analyzed under pull-off loading assuming a predefined defect in the structure. Initial damage is detected via the virtual crack closure technique implemented in the finite element analysis and is assumed to be the characteristic variable to compare the different behaviors. Experiments are conducted to validate the analysis method and to provide evidence that the use of nanocomposites at the structural level is effective and can be implemented. It can be seen that the use of nanocomposites in the manufacturing process of composite stringers will delay failure from occurring providing an alternative design solution to delay delamination in such composite structures typically used in the aerospace industry.