A Novel Approach to Delamination Study Under High‐Cycle Bending Fatigue: Investigation of Stiffness Degradation of Laser‐Cut <scp>GFRP</scp> Composites

ABSTRACT The propagation of delamination and stiffness degradation in laser‐cut, thermoset glass fiber‐reinforced composites (GFRC) under bending fatigue has not been comprehensively analyzed, particularly in terms of their long‐term performance. This study introduces a novel approach by integrating the cohesive zone model (CZM) and continuum damage model (CDM) with Hashin failure criteria to predict and validate delamination mechanisms in laser‐cut open‐hole GFRC. Unlike previous studies that analyzed these damage mechanisms separately, this research presents a combined computational‐experimental framework that correlates numerical stiffness degradation with experimental three‐point bending fatigue results. Two distinct layup orientations, [90/0/90/0] and [45/−45/45/−45], were analyzed under fatigue loading conditions of 20,000 and 40,000 cycles. The findings demonstrate that the proposed numerical framework can effectively predict delamination initiation, propagation, and stiffness degradation trends, closely matching experimental results. This study offers a validated methodology for fatigue life estimation of open‐hole GFRC, paving the way for more precise durability assessments in composite structures used in aerospace, marine, and automotive applications.