Size effect on stress-intensity factors of CNS specimen with an interface crack subjected to mixed-mode loading

A three-dimensional finite element analysis is carried out by using a compact normal and shear (CNS) specimen with various kinds of specimen size. The complex stress intensity factor K associated with an elastic interface crack is evaluated by the virtual crack extension method. The effect of Young's modulus and Poisson's ratio on stress intensity factors is discussed under various kinds of mixed-mode loading. It is predicted that the stress intensity factors would vary with the specimen size. Then, the size effect on stress-intensity factors is discussed. A simple evaluation method for stress intensity factors is needed in the fracture toughness test. Therefore, a polynomial fit is proposed to evaluate the stress intensity factors at the midsection of a CNS specimen with an interface crack subjected to mixed mode loading. It is possible to evaluate the stress intensity factors of a CNS specimen with high accuracy by the present polynomial evaluation.