Delamination configuration-induced compressive failure evolution and load-carrying degradation mechanisms of wind turbine blade spar-cap laminates

Abstract Delamination-induced local instability, damage evolution, and compressive load degradation are critical issues affecting the structural performance of wind turbine blade spar-cap laminates. In this study, a three-dimensional nonlinear finite element model incorporating matrix nonlinearity, intralaminar progressive damage, and interfacial delamination propagation was developed to investigate the effects of delamination configurations on compressive failure evolution and load-carrying capacity. The influences of delamination size, through-thickness position, and multiple-delamination spatial configuration were systematically examined. The results show that initial delamination reduces local interlaminar constraint, triggering sub-laminate buckling and subsequently promoting interfacial damage propagation and load-transfer degradation. Increasing delamination size continuously decreases the ultimate load-carrying capacity, whereas moving the delamination toward the laminate mid-plane improves local stability by balancing the bending stiffness of the separated sub-laminates. For multiple delaminations, increasing the in-plane spacing between coplanar delaminations partially restores the constraint and load-transfer capability of the intact material region, while overlapping delaminations exhibit a pronounced non-monotonic through-thickness spacing effect. These effects can be attributed to the changes in effective unconstrained length, sub-laminate stiffness distribution, and spatial constraint interactions among multiple defects, which collectively govern local buckling, interfacial damage evolution, and final load degradation. The findings provide mechanistic insights into the assessment of delamination-induced damage and residual load-carrying capability of composite wind turbine blade structures.