A mode I-II-III decomposed cohesive zone model for 3D simulation of delamination propagation in laminated composite materials
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State-of-the-art simulation models for delamination prediction based on the cohesive zone model approach cannot distinguish between mode II and mode III components. Moreover, mode II properties are usually lower than those of mode III. As a result, shear opening mode is conservatively treated as mode II in the current constitutive models of all the commercially available finite element codes. However, the assumption of identical fracture toughness for II and III shear mode openings, and their combination, is not the most accurate approach. An algorithm developed by the authors of this contribution [1] determines the direction of crack propagation for arbitrarily shaped delamination fronts in 3D structures. The method can be directly implemented in a user-defined element subroutine and be evaluated at integration point level at the execution time of the analysis using element information. This algorithm implemented in conjunction with the in-house cohesive zone model is used in this work to develop a formulation that considers the decomposition between mode II and mode III. Thus, the developed cohesive zone model allows defining a mode I-II-III dependent interlaminar fracture toughness. The capacity of the new formulation to overcome the limitation of current constitutive models, which generalize the shear fracture mode properties, was demonstrated by making a comparison between results obtained from the new formulation and the existing formulation [2]. The new formulation was tested and verified by means of finite element analysis using one cohesive element subjected to various case studies of prescribed loading configurations. The resultant one-dimensional cohesive law at the integration points corresponds to the parameters of either one of the pure modes or a combination of various modes depending on the loading configuration of the applied displacement and the direction of crack propagation.