Interlaminar Fatigue Life Estimation of Composite Laminates and Substructures Under HCF and VHCF Loads: A Generalized Computational Framework

ABSTRACT The current research work presents a generalized and thoroughly validated finite element (FE) methodology to predict the mixed‐mode delamination‐induced fatigue life (S–N curve) of composite laminates and substructures under high cycle fatigue (HCF) and very high cycle fatigue (VHCF) loads. A novel fatigue damage initiation (FDI) model is developed using the G–N curve obtained from coupon‐level fracture fatigue tests. The proposed FDI model is coupled with a fatigue damage propagation (FDP) model to predict the fatigue life of composite laminates and substructures. Besides, contrary to the typical ΔG = ( G max − G min )/ G c approach used as a crack driving force in FDP formulations, to capture the load ratio ( R ratio) effects on the fatigue failure, based on the similitude principles, is used as the crack driving force. The proposed fatigue damage algorithm is implemented using the cohesive zone formulations in Abaqus/Explicit via a VUMAT subroutine and validated against the experimental G–N curve at damage initiation and S–N curve until final failure for both individual and mixed‐mode loading conditions. Finally, the implemented FE methodology is extended to predict the fatigue life of a composite cylinder subjected to Brazier‐like crushing forces, demonstrating the proposed model's applicability to complex substructures under the loads that induce mixed‐mode failure. Highlights A novel fatigue damage initiation (FDI) model is proposed based on experimental G (energy release rate)–N (number of cycles to damage onset) curves and validated under individual modes. Mixed‐mode G–N curves at damage initiation are successfully predicted using individual‐mode G–N curves, eliminating the need for mixed‐mode experimental fracture fatigue tests. Contrary to the typical formulations used as a crack driving force in the propagation damage model, is adopted based on similitude principles to capture the R ratio effects on the crack growth rate. The FDI model is coupled with a fatigue damage propagation (FDP) model and validated for predicting the S–N curves of composite laminates and substructures.