Influence of Experimental Set-Up and Plastic Deformation on the Shaft-Loaded Blister Test
S Goldfarb, E P. O'Brien, Christopher C. White
The effect of film thickness, substrate hole diameter, and shaft tip diameter on the applied strain energy release rate, G, of a thin film was measured using the shaft-loaded blister test. Test specimens consisted of plies of Kapton pressure sensitive adhesive tape adhered to a rigid glass substrate. The effect of plastic yielding at the contact area between the film and shaft tip was investigated by measuring the load, displacement (blister height), and blister radius and calculating G from these different equations: (1) load-based, (2) hybrid, (3) displacement-based, and (4) combination. The film thickness and the shaft-tip diameter influenced the magnitude of the applied load, film stress, displacement, and therefore the amount of plastic yielding at the contact area. Plastic deformation at the contact area affected the displacement and lead to inconsistent values of G when the displacement value was included into the calculation. However G calculated from the load-based equation, although dependent on film thickness, was independent of the size of the shaft-tip diameter and therefore the plastic yielding at the contact area.