Micromechanical crack growth-based fatigue damage in fibrous composites

• Fibre–matrix interface debonding phenomenon is examined.
• Fracture mechanics approach is applied to fibre debonding.
• Fatigue crack growth simulates the progressive fibre detachment.
• Damage under cyclic loading is adopted for the matrix material behaviour.

A partially debonded fibre can be analysed as a 3-D mixed Mode fracture case, 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 research, the above mentioned case is firstly examined from the fracture mechanics theoretical point of view, and the effects of the stress field in the matrix material on the Stress Intensity Factors – SIFs – (associated to the crack representing the fibre–matrix detachment) are taken into account. Fatigue effects on the matrix material are accounted for by means of a mechanical damage, quantified through a Wöhler-based approach. 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 experimental data found in the literature.