Aamir Dean, M. Hematipour, Pavan Kumar Asur Vijaya Kumar, Raimund Rolfes
Structural adhesives are essential in wind turbine blades, where bonded joints are subjected to complex static and cyclic loading and are prone to fatigue-driven failure. Recently developed short fibre-reinforced polymeric (SFRP) adhesives offer enhanced mechanical performance, but their fracture behaviour is strongly influenced by fibre orientation and anisotropy. This study presents an experimental-numerical framework for predicting quasi-static and fatigue fracture in SFRP adhesives using a phase-field approach. An experimental campaign, including quasi-static and tension-tension fatigue tests with full-field strain measurements, reveals pronounced anisotropic elasto-plastic behaviour, orientation-dependent fatigue life, and distinct damage mechanisms under monotonic and cyclic loading. Based on these observations, an anisotropic phase-field model for ductile fracture is developed and coupled with an invariant-based transversely isotropic elasto-plastic constitutive formulation with pressure sensitivity and non-associative plastic flow. Fatigue effects are incorporated through a thermodynamically consistent degradation of fracture toughness driven by accumulated energy dissipation. The model is implemented within a finite element framework and validated against experiments through simulations of dog-bone and single-edge notched specimens. The numerical results show very good agreement with experimental stress–strain responses, S-N curves, and crack initiation and propagation behaviour, demonstrating the capability of the proposed framework to predict the durability of SFRP adhesive joints under static and cyclic loading.