Rubber cord adhesion inflation test: Influence of envelope/ confinement friction

The Rubber Cord Adhesion Inflation Test (RCAIT), has been previously introduced as an alternative test protocol to traditional pull-out tests for measuring the toughness of rubber matrix to metal reinforcement interfaces. A pressurized fluid is injected in between the matrix and reinforcement in a non-adherend region to initiate and propagate a crack along the specimen. A selfsimilar crack propagation regime hypothesis is assumed and the critical strain energy release rate is obtained from a simple energy balance analysis. However, to force the crack propagation along the specimen and prevent the development an aneurism in the rubber enveloppe, a confinement tube is used. A lubricant allows "free" longitudinal expansion of the rubber envelope during the contact. Combined theoretical, numerical, and experimental analyses are then proposed here to assess the effectiveness of lubrication conditions. Our results indicate an inversely proportional scaling between the elongation gradient and the friction coefficient in the pre -crack region. The observation confirms the validity of frictionless contact with a greased contact. Meanwhile, the steady-state crack growth assumption holds with the introduction of contact friction.