Fracture Mechanics of Unidirectional Composites Using the Shear-Lag Model I: Theory

Using the shear-lag model, we have solved for the crack-tip stress concentrations in double-edge notch and center notch unidirectional composites of finite width. From the stress-state solution, expressions are derived for strain energy release rate due to crack propagation through the fibers and due to crack propagation parallel to the fibers. It is pro posed that these new equations, which include geometric correction factors, may be used for fracture mechanics analyses of unidirectional composites and that their use will pro vide better physical insight into composite fracture. Because the heterogeneous nature of composites is specifically taken into account, it is suggested that these new equations are superior to ones derived from classical fracture mechanics or from stress-state solutions for homogeneous materials.