Telephone cord blisters driven by pockets of energy concentration in multilayer films

Telephone cord blister (TCB) propagating forward with periodic wavy boundaries is commonly observed in thin films with weak adhesion and large compressive stresses. Under the mechanical assumption [1, 2] that the formation and development of TCBs are driven by an external energy source in addition to the initial residual strain energy in the un-delaminated film, new mechanical models are furthermore developed in this work to characterise the morphology parameters for the multilayer TCBs exhibiting small and large deformations. Theoretical predictions of the morphology parameters are in good agreement with extensive experimental results shown in [3, 4]. Mechanical conditions are also revealed for the TCB formation in multilayer films. This work provides a mechanical understanding of blister development, coating adhesion and blister shape, and it can guide improvements in the industrial design of multilayer coating material systems.