A fracture mechanics methodology for slow crack growth in thin polyimide films

Abstract

A fracture mechanics methodology for assessing the influence of stress and defect size on the structural integrity and life expectancy of thin polyimide films is presented. The approach is a synergistic one that combines fracture mechanics analyses and experiments to quantify slow crack in the films. A viscoelastic fracture model is used to deduce the crack growth history from load-point displacement records measured during long-term fracture tests of the films. The rate of crack growth is found to depend very strongly upon the crack driving force as measured by the stress intensity factor. Hence, small changes in the stress intensity factor can produce dramatic changes in the crack growth rate in the materials investigated.<>