Embedded Flaws in Unidirectional Composites

An analytical model is developed for the determination of displacement and stress distributions in a finite three-dimensional unidirectional composite with broken fibers forming an embedded planar crack, normal to the fibers and the loading. In order to reduce the complexity of the elasticity formulations, some assumptions have been made as to the physically significant stresses to be retained; fibers carry the tensile load and the matrix carries only the shear force. These assumptions simplify the partial differential equations into a set of differential-difference equations. The governing equations are solved for various crack configurations as the composite material is subjected to a uniform tensile load along the fiber direction. The results for different shapes of the embedded crack show that a crack tends to extend first at the centers of its straight edges and eventually attains a circular shape. © 1991