Crack propagation along interface having randomly fluctuating mechanical properties during DCB test finite difference implementation - Evaluation of Gc distribution with effective crack length technique

A finite difference numerical scheme is implemented to study the crack initiation and propagation along a Double Cantilever Beam specimen assuming either elastic-brittle interface or elastic perfectly plastic behavior. The finite difference calculations are first compared to known analytic solution to evidence the benefits and limits of this numerical method. Then randomly fluctuating interface properties along the crack propagation path is considered to investigate the effect of variability on the force versus opening displacement evolution measured at a macroscopic scale. The local fluctuation of the critical Strain Energy Release Rate (SERR), Gc, could be estimated using the effective crack length technique. However, local minima of the critical strain energy release rate induce unstable crack propagation so that the weakest regions of the interface are not probed. Also, fluctuation of interface properties induce distortion of Gc distribution which could lead to non-conservative evaluation of the interface toughness.