Fracture load prediction of components weakened by symmetrical and asymmetrical rounded-tip V-notches using the phase field method

Abstract

This paper presents an investigation into the fracture behavior of the engineering components weakened by V-notches, using the phase field method. The study employs a combined experimental-numerical approach to evaluate the effectiveness of the phase field model to predict the fracture load of samples with different materials under mode I loading. In the first step, symmetrical rounded-tip V-notched (RV) Compact Tension (CT) samples made of epoxy resin were fabricated and experimentally tested to determine their corresponding fracture load and fracture path under mode I loading in different notch geometrical configurations (e.g., opening angle and notch-tip radius). Experimental results of CT samples were then compared with phase field simulations. The phase field simulation results were further validated against the experimental data from the literature on three-point bending (TPB) specimens made of graphite. There was a close agreement between the numerical and experimental fracture loads across all tested materials. Notably, the phase field simulations showed higher accuracy for RV notches with larger radii when compared to experimental results. Furthermore, the study evaluated the effect of asymmetry in notch geometrical configurations on the strength variation of the components containing notches. Mode mixity parameter ($M_V$) was computed for each one of the assessed samples by utilizing the magnitude of stress ahead of the notch tip. The effect of opening angle and notch-tip radius were evaluated for RV-notches to determine the contribution of each parameter to the variation of the fracture load due to the existence of asymmetry. The study showed that the highest amount of strength reduction due to asymmetry happened in RV-notches with smaller notch radius. Besides, it was found that the fracture load decreased by increasing asymmetry angle. However, the results showed no significant further reduction in strength after reaching a certain threshold of asymmetry.