An evaluation of the stress intensity factor in functionally graded materials

Functionally graded materials (FGM) are characterised by variations in their material properties in terms of their geometry. They are often used as a coating for interfacial zones to protect the basic material against thermally or mechanically induced stresses. FGM can be also produced by technological process for example butt-welding of polymer pipes. This work is focused on a numerical estimation of the stress intensity factor for cracks propagating through FGM structure. The main difficulty of the FE model creation is the accurate description of continual changes in mechanical properties. An analysis of the FGM layer bonded from both sides with different homogenous materials was performed to study the influence of material property distribution. The thickness effect of the FGM layer is also discussed. All analyses are simulated as a 2D problem of an edge cracked specimen. In this paper, the above effects are quantified and conclusions concerning the applicability of the proposed model are discussed