Bulge and blister testing of thin films and their interfaces
Abstract
The aim of this work is to refine the understanding and application of the bulge and blister techniques, which are useful for studying mechanical properties and adhesion of thin-film materials. In the bulge experiment, the deflection of a pressurized, free-standing thin film window is analyzed to determine the film's mechanical properties. We perform a thorough analysis of the deflection of linearly elastic, membrane-like windows, treating both residual strain and the strain resulting from out-of-plane stretching. Comparing solutions from various sources, we establish a generalized equation relating a window's deflection to its dimensions, mechanical properties, and the applied pressure. We analyze bending stresses near the window edge, and establish techniques for studying plasticity using the bulge technique. In the related blister technique, pressure is increased until the film debonds from its substrate, forming a circular "blister" which grows stably. The energy expended debonding the film, which provides a measurement of adhesion, can be determined from measurements of pressure and deflection. We derive a generalized relation for the energy release rate, and analyze the mode mixity generated by the experiment. The design of a blister test apparatus is described, with emphasis placed on the construction of a stiff system which permits stable blister growth and accurate measurement of blister volume. We describe techniques for fabricating free-standing windows. Sources of error in bulge test results are examined, and techniques for analyzing and interpreting experimental data described.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1999
- Bibcode:
- 1999PhDT.......164H