Modeling end notched flexure tests to establish cohesive element Mode II fracture parameters

The objective of this work was to establish Mode II fracture parameters for cohesive elements that can be further utilized to evaluate Mode II interfacial fracture strength of polyurea/AISI 4340 steel composite structures. To obtain the fracture parameters, end notched flexure (ENF) tests were conducted to validate proposed finite element models. The fracture behavior observed from the tests was highly nonlinear and large plastic deformations were involved during crack formation and propagation. A strain incompatibility model was introduced to describe the nonlinearity prior to fracture. This nonlinear and plastic behavior made Linear Elastic Fracture Mechanics (LEFM) approaches not applicable to approximate the fracture parameters. As a result of these experimental observations, finite element analyses of the ENF tests were performed to develop the necessary fracture parameters for cohesive elements selected to replicate the failure modes. Good agreement between the selected numerical models and experimental data was observed.