Modelling of Fracture Toughness in Steel Laminates with a Finite Element Method


Abstract: The fracture toughness of laminates in which both phases are ductile is modeled with finite element analyses in terms of J_{IC}. The models employed were an exact analogue of compact tension test pieces loaded longitudinally at pinholes, transverse to the crack plane. This study focused on the verification of the model in monolithic samples, the simplest form of which was 2-dimensional (plane strain), and the most elaborate version of which was a 3-D layered structure. Adaptation of the model to laminates showed that it is possible to predict delamination if the individual layers are glued together with a certain interfacial strength. The fracture toughness of laminates, J_{IC}, is predicted with and without delamination with the use of a fracture criterion based on a critical value of load line displacement. This critical value derived from the experiment, and the fracture toughness of steel laminates with layer properties of low-C and medium-C steels are predicted successfully for 2 volume fractions. It is further found that the fracture criterion, which was based on a critical value of LLD, can well be based on a critical value of plastic zone size. This has the advantage that the critical value of plastic zone size and hence the J integral can be predicted with FEM analysis.

Keywords: Finite element method, J integral, Laminates, Interfacial strength, Delamination, Load line displacement, Plastic zone size

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