Effect of notch corner shapes on mechanical behaviour and failure mechanism of notched timber beams

Abstract

This study investigates the impact of various notch corner shapes on the load-bearing capacity of timber components of timber chocks as one of standing support systems in underground mines. Three notch configurations including rectangular-rounded, double-rectangular and double-rounded types created from spotted gum, a common Australian hardwood, are subjected to three-point bending tests. In this investigation, Digital Image Correlation is used which aims to visualise displacement and strain fields, offering insights into crack initiation, and coalescence. Furthermore, various timber design standards are implemented to compare the load-carrying capacity of notched beams with experimental results, aiming to estimate the performance of timber chocks. The results demonstrate the benefits of notches with rounded corners compared to sharp notches exhibiting higher deflection and resistance to tensile strain perpendicular to the grain while an increase in the load-carrying capacity is marginal. Moreover, rounded corners offer the highest fracture energy, accounting for both elastic deformation and the energy which are needed for crack propagation and plastic deformation.