An extended phantom node method study of crack propagation of composites under fatigue loading

In the current study, the traditional phantom node method is extended for crack propagation modeling of composite materials under fatigue loading. A fatigue damage variable, directly related to experimental crack propagation rate, is combined with the static one for interface property degradation, while a bilinear cohesive law considering damage initiation is used for quasi-static cracking modeling. The presented fatigue phantom node method is coded as an user-defined element in ABAQUS and its numerical implementation, including global data, element connectivity and, especially, a pre-cracking treatment, has been discussed in detail in consideration of limitations from the commercial FE software. The proposed method has been validated based on mode I, mode II and mixed mode fatigue crack propagation experiments and, based on that, influences of interface strengths and element size on crack propagation rate evaluation have been investigated briefly.