The fracture behavior of unidirectionally fiber-reinforced composites is the principal focus of this paper. The model proposed here is three-dimensional and accounts for the effects of local fiber-crack interactions on spatial variations of crack tip behavior. The model also consistently accounts for the effect of composite anistropy by embedding a penny-shaped crack in an orthotropic composite medium. Three factors are identified that influence the reductions of stress intensity factors (SIFs) due to fiber bridging: a dimensionless configuration constant, a fiber distribution pattern, and a fiber volume fraction. The model reveals that the fiber distribution pattern does not alter the spatial mean of the SIFs, although it does affect the oscillational amplitude. The dimensionless configuration constant determines the extent of the bridging effect and provides guidance regarding possible avenues for enhancing bridge toughening. The design curve of SIFs (retarded by fiber bridging) vs the fiber volume fraction shows that the isotropic and orthotropic solutions differ just slightly from each other. However, the energy release rate obtained by an isotropic analysis (widely claimed to be the equivalent of SIFs in bridging models) could, significantly underestimate the bridging effect.
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