A simple method for evaluating the effect of fiber bridging on the stress field in the vicinity of a crack tip in Double Cantilever Beam (DCB) specimen of unidirectional fiber reinforced composite was proposed. In this method, each bridging fiber was approximated by a beam, and the force and moment acting on the fiber was calculated using conventional beam theory. Stress intensity factor at the crack tip was evaluated by means of the finite element method taking into account the axial force and bending moment carried by the bridging fibers. The analysis was carried out for several types of bridgings. Results of the analysis showed that shorter fiber and/or the fiber situated more behind the crack tip reduced the stress intensity factor much, because those fibers were thought to be subjected to large displacement and brought about large force in crack closing direction. Moreover, when bundled fibers bridged the crack, i.e., when the bridging fibers were connected and deformed as one composite beam, reduction in stress intensity factor was striking. This shows that bundling of bridging fibers plays an important role in stress shielding.
