On an annular crack near an arbitrarily graded interface in FGMs.

• Arbitrarily graded shear modulus and Poisson's ratio in the FGMs is considered. • Analytical solutions of the stress intensity factors are obtained. • A practical example of an annular crack in a real Epoxy-Glass FGM with measured data of material properties is analyzed. • The error due to the special gradation can be significant if the crack is very closed to the graded interface with large thickness. Annular cracks can be generated during the fabrication of materials and around the pre-existing defects. Previous works on the annular crack problems were most limited to homogenous materials. This paper extends the analysis and examines the axisymmetric problem of a flat mixed-mode annular crack near and parallel to an arbitrarily graded interface in functionally graded materials (FGMs). The crack is modelled as plane circular dislocation loop and an efficient solution for dislocation in FGMs is used to calculate the stress field at the crack plane. The three-parts mixed boundary value problem is solved by a series expansion method. Analytical solutions of the stress intensity factors are obtained. Compared with many other existing analytical treatments to the crack problems in FGMs with the assumption of special gradation, the present method can consider arbitrarily graded shear modulus and Poisson's ratio. It is shown that the present solution can reduce to existing solutions in literatures for annular crack in homogenous materials. Numerical study is conducted to investigate the fracture mechanics of annular crack in FGMs. A practical example of an annular crack in a real Epoxy-Glass FGM with measured data of material properties is also considered. [ABSTRACT FROM AUTHOR]