Influence of anisotropy on the energy release rate $G_{\rm I}$ for highly orthotropic materials

The paper presents results of a numerical analysis concerning the energy release rate, $ G_{\rm I}$, for highly orthotropic materials such as composites, laminates or wood. The values of $ G_{\rm I}$ were calculated using the Adina v. 8.1 Finite Element Method (FEM) program. Different material models were considered to establish the influence of anisotropy on $ G_{\rm I}$. Two-dimensional (2D) and three-dimensional (3D) isotropic and anisotropic models were employed to study the performance of a Double Cantilever Beam (DCB) with various crack length-to-thickness ratios. It was reported that the smaller the ratio, the bigger the difference between the energy release rates $ G_{\rm I}$ calculated for the isotropic and anisotropic (transversal isotropic and orthotropic) material models. Thus, it is important that a fracture or fracture toughness analysis should be based on the transversal isotropic and orthotropic models and it should take into account anisotropy.