Buckle-driven delamination of thin film and the influence of the Casimir or van der Waals force interaction

Indentation test is becoming increasingly used to quantitatively assess the thin film interfacial adhesion for its simplicity and ability to mechanically probe the smallest of solids. The conventional technique is based on the analysis of a combination of linear elastic fracture mechanics (LEFM) and simplified post-buckling theory. In this paper a full post-buckling response of thin film is investigated by FEM calculation; the contributions of double-buckling to the indentation test is discussed. The results show that double-buckling needs more energy than single-buckling case thus lead to a greater value of strain energy release rate. Finally, the influences of the Casimir or van der Waals interaction on the post-buckling behavior between the thin film and substrate are considered.