Fatigue Crack Propagation Simulating Fibre Debonding in Cyclically Loaded Composites

A partially debonded fibre can be analyzed as a 3-D mixed Mode fracture problem for which the fibre-matrix detachment growth – leading to a progressive loss of the composite's bearing capacity – can be assessed through classical fatigue crack propagation laws. In the present study, the above mentioned problem is firstly examined from the theoretical point of view, and the effects of the stress field in the matrix material on the SIFs (associated to the crack representing fibre-matrix detachment) are taken into account. Suitable fatigue crack propagation laws for mixed mode SIFs are employed in order to quantify the crack growth rate corresponding to the fibre-matrix debonding growth rate, while the matrix material undergoes a mechanical damage quantified through a Wöhler-based approach to fatigue. A damage scalar parameter aimed at measuring the debonding severity during fatigue process is also introduced. Finally, some numerical simulations are performed, and the obtained results are compared with results found in the literature.