An experimental setup for characterizing subcritical debonding of materials interface under mixed mode fatigue loading

A mixed mode bending experimental setup was developed for quantifying the subcritical debonding growth behavior for materials interfaces under a full spectrum of loading mode mixity. In the experimental system, the control program calculates and adjusts the cyclic bending forces to maintain a constant phase angle at the prescribed value. The relationship between the subcritical crack growth rate and the applied strain energy release rate range is obtained by post-processing the experimental results with analytical formulas. As a preliminary application example, a phase-angle dependent power-law model was constructed for the subcritical debonding growth rate of the Al-epoxy interface. It was observed that both the logarithm of the scaling constant and the power-law exponents of the subcritical debonding growth model exhibit linear relationships with the phase angle.