Stress intensity factors for interface cracks between orthotropic and monoclinic material

Different expressions are used in the literature for the stress intensity factors of interface cracks between anisotropic material. In particular, two of these approaches will be discussed and compared for orthotropic and monoclinic materials. Relations between the stress intensity factors will be found. Expressions for the interface energy release rate G_i{mathcal{G}_i} are presented. Although the expressions appear different, they are shown to be the same by using the relations between the stress intensity factors. Phase angles are defined which may be used in a fracture criterion.