Thin films are usually submitted to high residual compression stresses which cause
them to delaminate and buckle. We focus on the case in which delaminated areas
take the form of long rectangular strips. The most commonly observed buckling
equilibria that develop on such strip-delaminated areas are the straight-sided wrinkle,
the row of bubbles, and the telephone cord wrinkle. An analytical model, based on
elastic rods with hinges and taking into account the contact between film and
substrate, is set up for the study of the post-buckling regime of the transition
from straight-sided wrinkles to bubbles. The existence of snap-through is
investigated; previous numerical studies revealed that this phenomenon can
sometimes occur. The present analytical approach excludes numerical artifacts
that can easily arise due to the high sensitivity of this problem to initial
imperfections. The model reveals a critical bubble aspect ratio associated
with the snap-through, and the existence of several simultaneous bubble
equilibria.
Keywords
mechanical properties of thin films, static buckling,
instability, variational and optimizational methods,
elastic rods with hinges models