Method for Analyzing the Effect of Fiber Bridging on the Stress Field in the Vicinity of Crack Double Cantilever Beam Specimen of Unidirectional Fiber Reinforced Composite

摘要

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