Mode I debonding under large deformation conditions including notes on cleavage-peeling transition

Abstract

Peeling and cleavage are common load cases for studying and evaluating adhesion between materials. The former is suitable for testing adhesion of thin or highly flexible materials for which the bending energy is negligible while the latter uses the rate of released bending energy as a measure of fracture energy. Their data reduction schemes are very different, which could lead to situations where peel-cleavage transition cases are misinterpreted. In this work, two analytical frameworks allowing transition between peel and cleavage configurations to be accounted for, are exploited. The first is an elliptic integral based solution, which in the present study is enhanced by the elastic foundation formulation to mimic interfacial reaction forces to external loading. The second is built on a pseudo-linear equivalent system, which allows representation of geometrically non-linear problem through a number of simple, linear segments. Both solutions are successfully confronted against each other and a geometrically non-linear finite element formulation. In addition to the analytical framework, a number of phenomenological insights into the transition are gained. These are presented as master curves relating geometrical and material parameters to the shape of the steady-state fracture response and the rotation of the load application point through the spectrum from cleavage to peeling. The disclosed results could prove valuable when designing, evaluating or analyzing mode I fracture of materials and structures of finite and non-zero bending stiffness.