Numerical analysis of crack-tip fields in functionally graded materials with a crack normal to the elastic gradient

The nature of the singular field around the crack in functionally graded ma terial (FGM) is analyzed parametrically using finite element method. The nu merical simulations are carried out by varying the location of the crack in the graded region for different material gradients. Using linear material property variation in the gradient zone, the influence of material gradient and the crack position on the fracture parameters such as complex stress i ntensity factor (SIF) and energy release rate are studied. The crack openin g displacement profiles of FGM are compared with the homogeneous and bimate rial counterparts. The analysis shows that the fracture parameters of FGM a pproach that of the bimaterial as the material gradient is increased, regar dless of the position of the crack in the graded region. The extent of appl icability of the homogenous crack tip fields around the crack in FGM is ana lyzed, and the results show that the size of the homogeneous field reduces with the increase in material gradient. Static fracture experiments are con ducted on epoxy based FGM to determine complex SIF with electrical strain g ages, using the homogeneous field equations to convert the strains to SIF. The measured SIF values compare favorably with the numerical results provid ing a limited experimental validation of the computations and the use of ho mogeneous field for FGM. (C) 2000 Elsevier Science Ltd. All rights reserved .