Providing a virtual material for simple estimation of fracture in U-notched highly orthotropic specimens with nonlinear behavior under mixed mode I/II loading

Abstract

This research investigates the fracture toughness of U-notched Russian pine specimens with highly orthotropic nonlinear behavior under mixed mode I/II loading conditions theoretically and experimentally. The notch strength of orthotropic specimens is successfully predicted by introducing a novel two-step model of material simplification. Adopting this model, the nonlinear orthotropic material is equated with a virtual linear elastic isotropic material by coupling the Virtual Isotropic Material Concept and the Equivalent Material Concept. Therefore, the linear elastic notch fracture mechanics criteria, such as the mean stress and point stress models, can be basically employed to predict the notch fracture toughness of U-notched specimens made of nonlinear orthotropic material. Accordingly, the experimentally obtained notch strength of nonlinear orthotropic samples is predicted in the form of fracture limit curves and the curves of fracture initiation angle. It is shown that the two-step model proposed can be successfully applied for mixed mode I/II fracture estimation of notched orthotropic specimens with nonlinear behavior.