Fracture parameters and crack initiation Assessment Employing Mixed-mode I/II Fracture Criterion in Laminate Composites Using Digital Image Correlation Method

The present study aims to have fracture parameters, such as stress intensity factors (SIFs) and J-integral, as well as the crack initiation angle, extracted through the utilization of a novel mixed-mode (I/II) fracture criterion founded on the maximum energy release rate (MERR) and maximum tangential stress (MTS). The digital image correlation (DIC) method is employed in the analysis of crack behavior. Of note, several key findings are highlighted by our research. Results show a slight decrease in the mode I stress intensity factor (KI) with an increase in the crack inclination angle (phi). Interestingly, a bell-shaped curve characterizes the mode II stress intensity factor (KII), with its peak occurring at phi = 45. Comparison of experimental outcomes with finite element (FE) based modeling reveals consistent trends in both KI and KII from both sources. The comparison of experimentally determined crack initiation angles with predictions from the MERR and MTS criteria offers insightful observations. For phi <= 30, both criteria closely match experimental outcomes, as the crack initiation corresponds to phi. However, for phi > 30, these criteria underestimate the crack initiation angles, leading to a slower decrease in kink angles compared to observations. Further analysis involves a comparison between the two criteria and experimental results. Here, MERR emerges as being more accurate in prediction than MTS. Lastly, Simpson's rule is employed to calculate the J-integral, contributing to a comprehensive understanding of crack behavior. The reliability of the new mixed-mode fracture criteria and the DIC method in evaluating crack tip conditions and predicting minor kink angles is established by our study. Not only is understanding enhanced by our findings, but practical applications in predicting crack initiation and behavior in complex materials are also offered.