Fracture analysis for a sub-interface Zener–Stroh crack in a bi-material plate under small-scale yielding condition

• The sub-interface fracture behavior has been simulated by Zener–Stroh crack mechanism for a bi-material plate.
• The plastic zone correction ahead of the crack tips by the mixed mode Dugdale model with Von Mises yielding criterion.
• The shear modulus ratio of the two materials has great effect on the normalized plastic zone size and CTOD.
• The influence of material properties will be enhanced by moving the crack closer to the material interface.

The fracture behavior of a Zener–Stroh crack near a bi-material interface is investigated under the small-scale yielding condition. The plastic zone area is thus modeled by a modified Dugdale model, in which the Von Mises yielding criterion is applied in the yielding zone. The initial crack problem is formulated into a set of singular integral equations by dislocation method so that the stress intensity factors can be calculated numerically. The yielding zone size or the plastic zone size (PZS) and the crack tip opening displacements (CTOD) at the blunt and sharp tip are evaluated for the current Zener–Stroh crack. Numerical examples are given to show the effects of material properties and crack-interface distance on the normalized PZS and normalized CTOD of the Zener–Stroh crack. It is found that the Zener–Stroh crack is easier to propagate when it locates in the “softer” phase of the bi-material structures. For a Zener–Stroh crack, the crack propagation always starts from the sharp tip. By carrying out the plastic zone correction, failure analysis becomes more accurate thus able to avoid over-estimation in composite structure design and enhance the service life of the structure.