A novel method for the in situ repair of subcritical damage in complex composite structures (T-joints) is demonstrated. In situ repair is achieved through the use of embedded microvascular networks within the structure. Once failure occurs, the embedded vascules are ruptured, providing a route for the injection of a repair agent directly into the damage site. The efficacy of these networks at infiltrating damage is assessed for a number of configurations of vascularized T-joints. The effect of vasculature on the mechanical performance of the component is assessed both numerically and experimentally. Two- and three-dimensional thermomechanical finite element analyses are performed to determine the influence of vasculature on thermal residual stresses and joint strength under 90 deg tensile (pulloff) loading. Failure mechanisms observed during 90 deg tensile pulloff testing agree well with the prediction from finite element analyses. In all cases, successful interaction of vascules with the damage is achieved, giving promise for the future applicability of these channels for in situ repair applications. Further optimization is required, but the vascularized deltoid configuration shows considerable promise for future industrial adaptation.