Mode II Delamination Toughness in Glass Fiber-Reinforced Polymers with Bridging Fibers and Stitching Threads

Abstract

This article presents results for mode II delamination resistance of fiber-reinforced polymers (FRP) using a recently developed internal notched flexure (INF) test. The study showed that the decrease of the compliance with the growth of delamination in the INF test was much less than that predicted by analytical or finite element analyses of the same configuration. The difference was mainly due to pronounced shear force interaction generated by bridging fibers and stitching threads between fracture surfaces. A new data-deducing method, named direct method with correction (DMC), was developed for establishing a delamination resistance curve (R-curve), which can take into account the effects of shear force interaction but does not require in situ measurement of crack growth length. The DMC was further examined using results from a series of INF tests with variation in test set-up configurations and types of glass fiber preform.