Large scale yielding in blister specimens

Abstract

Nonlinear von Karman plate theory was used for a consistent analysis of pressurized circular, island and peninsula blister specimens. The configurations that were considered ranged from linear plates to membranes. Interfacial energy release rates and fracture mode-mixes were extracted from the solutions. For a given pressure and all possible materials and delamination length to thickness (aspect, a/h) ratios, the peninsula blister provided the highest energy release rate, followed by the island and circular blisters. The extent of yielding in delaminating copper films with a range of thicknesses and an interfacial toughness of 100 J/m² was then examined. It was found that all configurations of the circular blister suffered from large scale yielding. The stress levels in the island blister were notably lower, especially for a/h=10, where yielding only occurred over about 10 percent of the delaminating copper layer. While extensive yielding was still present in peninsula blister configurations with a/h=100 and 500, there was none for a/h=10. A scheme for extending the utility of blister specimens to higher aspect ratios was suggested and analyzed.