The T-stress effect on the plastic zone size in a thin ductile material layer sandwiched between two elastic adherents

This paper investigates the crack tip plastic zone in a thin ductile layer sandwiched between two identical perfectly elastic adherents subjected to normal loading. The well-known Varias et al. model for calculation of the plastic zone length in a thin constrained elastic-plastic layer was extended by the second nonsingular term of the Williams expansion. A useful engineering formula for the length of the plastic zone has been deduced, where the mechanical properties of the substrates and the layer material as well as T-stress value are included. The proposed theoretical model was verified on the basis of numerical FEM calculations. The results obtained by the model are in good agreement with numerical data.