Photoelastic verification of certain recommendations for numerical modelling of fracture using the phase field method

The resurgence of Griffith ' s energy balance approach has propelled fracture studies through the numerical implementation of Phase Field Modelling (PFM). Although significant advancements have been made, there are issues which need attention. These include the computational complexity of solving an additional partial differential equation (PDE) and the requirement for an extremely fine mesh to resolve the crack topology accurately. While adaptive algorithms and open-source programs like FEniCS assist in alleviating some of these computational difficulties, the complexity of resolving crack topology continues to be a significant barrier. Experimental techniques like photoelasticity have been indispensable tool in the field of fracture mechanics and have also been instrumental in proposing key concepts in fracture literature. This study systematically validates the efficacy of the PFM in the context of brittle fracture by meticulously conducting stress field-based comparisons utilising photoelasticity. Insights gained from the study also provide nuanced perspectives on mesh refinement issues and the practical applicability of PFM within the domain of linear elastic fracture mechanics to predict crack initiation and propagation. The stress evolution in phase field (PF) models is studied using experimental isochromatic fringe features from a Single Edge-Notched (SEN) specimen. Through a meticulous analysis combining crack propagation path, crack initiation point, and isochromatic fringe features, some recommendations have been formulated and subsequently validated across different classes of problems, such as the four-point bend beam and asymmetrically loaded beam with holes, each marked by inherent complexities. With these recommendations, the computational demand in the PFM for resolving crack topology can be reduced without losing the accuracy of the solution.