On the fracture toughness testing for single-edge notched bend specimen of orthotropic materials

Majority of the fracture toughness tests on orthotropic materials reported in the literature are based on the testing methods developed for isotropic materials since there is no available testing standards specifically dealing with orthotropic materials. In this study, a systematic two-dimensional finite element analyses (2D FEA) of orthotropic single-edge notched bend (SENB) specimens are performed to evaluate the stress intensity factor (SIF) and crack mouth opening displacement (CMOD), which are two key parameters used in the fracture toughness tests. The analysis matrix covers a wide range of material orthotropy. Highly accurate regression solutions for SIF, CMOD compliance and its inverse function were developed as functions of orthotropy parameters. Applications of the proposed equations on experimental data are presented and further discussed. The research outcome is expected beneficial to the standardization of the fracture toughness testing on orthotropic composite materials such as wood, bone and unidirectional fiber-reinforced polymer composites.