Characterization Method of Thick Films Using the Bulge Test Technique

A new theoretical model considering the bending effect for the thick films (the ratio η of thickness to radius was larger than 1/80) using the bulge test method was established based on the energy method. The experiments of Ti films and PVDF films of different ratio η had validated the feasibility of the new theory. The universal applicability of the new theoretical model for different mechanical parameters (E and υ) was verified by FEM. The new expression of pressure-height could well predict the deformation of bulge test for the films with different thickness. As the ratio η increased, the competitive mechanism of bending energy gradually replacing stretching energy in the films was revealed. The modulus and the stress distribution of cross-section could be characterized correctly by the new theory for thick films using the bulge test technique. It will provide a powerful research tool to study the deformation mechanism of thick films in the bulge test.