Numerical study of fatigue crack growth considering out-of-phase mixed-modes in laminar composites

In this work, the effects of out-of-phase fracture modes are investigated in the fatigue propagation of a crack located in an weak interface between layers of a laminar composite. Elastic and elastic-plastic constitutive equations are adopted for the layers. Mode II loading is delayed from mode I by a phase angle. A plane strain model is used in the simulations. Fracture propagation process is taken into account by an irreversible cyclic cohesive zone model. The present work shows that a resultant stress intensity factor controls the crack propagation in elastic specimens. In elastic-plastic specimens, propagation also depends on the energy dissipated in the volume. It was possible to conclude that most of the dissipation occurs due to closure of the cohesive zone during unloading of the mode I. The phenomenon is related to the rotation of the plastic zone around the crack tip and it is controlled by the phase angle between fracture modes.

Automated summary

The study found that crack propagation in elastic specimens is controlled by a resultant stress intensity factor, while in elastic-plastic specimens, it also depends on the energy dissipated in the volume. The rotation of the plastic zone around the crack tip is related to the phase angle between fracture modes.