Progressive Damage Modelling of Notched Carbon/Epoxy Laminates Under Tensile Fatigue Loadings

This work aims to simulate the initiation and propagation of intralaminar and interlaminar damage in open-hole carbon/epoxy laminates subjected to tension-tension fatigue loadings. The model is defined in the framework of damage mechanics and implemented as a user material subroutine in Abaqus/Explicit. The intra-ply damage constitutive model is based on the previous works of Maimí et al. [1, 2], but extended to fatigue loadings, whereas the fatigue cohesive model by Turon et al. [3] is implemented into the explicit code following the work of González et al. [4]. Both damage models are controlled by a cycle jump strategy within the finite element code thereby improving the computational efficiency of high-cycle fatigue analysis. The experimental observations revealed that the fatigue response of notched carbon/epoxy laminates is strongly governed by the progressive failure of the matrix, consisting of mainly longitudinal matrix splitting in 0ºplies and delamination. These forms of damage alleviate the stress concentration at the hole and thus suppress fibre fracture. As a consequence, the laminate is significantly degraded but complete failure is never reached before 106 cycles even at stress levels of 75% of the ultimate strength. The numerical results show the model's capability to predict splitting cracks, delamination and its interaction under fatigue loadings, although at this stage the capability is only judged qualitatively.