Abstract: Delamination defects in the R-curvature region of L-shaped laminated plates are almost inevitable during manufacturing. Their location strongly governs the load-bearing capacity of the composite structure and therefore dictates the strength-reduction factor—a key index in damage-tolerant design of composites. To quantify this influence and clarify the attendant failure mechanisms, this paper first examines how delamination position affects both the bearing capacity and the failure mode of L-shaped laminates, and subsequently investigates the contribution of fibre-bridging to the ultimate load. Experimentally, four groups of L-specimens were fabricated, each containing a delamination at a characteristic site in the R-region. Four-point bending tests were conducted while a high-speed camera recorded crack initiation and propagation; load–displacement curves were logged simultaneously. Numerically, an enhanced cohesive-zone model incorporating a modified traction–separation law was developed to reproduce fibre-bridging. The model was calibrated and validated against the test data. With the verified model, a data-augmentation campaign was performed to build a full-field defect database for the R-region and to construct an ultimate-load envelope versus delamination position, thereby transforming scattered test points into a continuous design surface. To isolate the bridging effect, a “bridging-free” counterpart model was additionally created. Results show that defect location exerts dominant control: all delaminations started from the pre-implanted defect front, and the most critical position reduced the ultimate load by 37%. Fibre-bridging altered the failure pattern, yet owing to the large high-stress zone in the R-curvature, the increase in peak load was limited. The established mapping between delamination position and residual strength provides a quantitative basis for setting design allowables of L-shaped composite laminates containing delamination defects.