Peeling a rigid sphere from a stretched rubber substrate

Polymer coatings are an important technology where pre-stresses can develop during draping, drying, and cooling. This paper aims to quantify the impact that these stresses have on the indentation response. Spherical probe indentation is performed on a stretched and unstretched substrate where the evolution of the contact area is monitored. Consistent with previous works, it is found that the contact area becomes elliptical on stretched substrates. Further, it is observed that this ellipse dynamically evolves during the indentation and peel process. This change in contact area upon stretching is found to increase the apparent stiffness and decrease the adhesive response.