Fracture of Ceramics with Near Surface Gradient Residual Stresses
The fracture toughness and strength of ceramics can be improved with respect to monolithic ceramics by developing graded materials as laminates composed of periodic alternating layers of one material separated by layers of a second material. The second layer must contain residual compressive stresses which are induced during densification because of differential thermal contraction of the layers. The overall residual stresses increase the apparent fracture toughness of the laminate. However, most deleterious natural flaws and most of the damage induced in service by the environment, contact loading, wear, etc, are small cracks on the surface of the outer layer, so that the effect of the laminate residual stresses on these cracks should be rationalised to understand their behaviour. This work presents an analysis of the influence of the gradient residual stresses on the behaviour of surface cracks under bending and indentation in materials with outer layers either with tensile or compressive residual stresses.
Marc Anglada et al.
M. Anglada "Fracture of Ceramics with Near Surface Gradient Residual Stresses", Key Engineering Materials, Vol. 333, pp. 97-106, 2007