Crack deflection in compositionally graded Cu-W composites

Abstract Crack deflection for cracks situated perpendicular to the composition gradient in Cu-W stepwise-graded composites has been examined through a combination of experiments and numerical models. Graded composites fabricated by hot pressing were notched, they were fractured in bending, and the crack paths were observed. A finite-element model employing thermal and mechanical properties measured in monocomposition specimens was used to estimate the direction of cracking, by applying a maximum principal stress criterion. The model was qualitatively successful in predicting the macroscopic direction of crack deflection, even for composites that fractured in a primarily ductile mode. The model shows that residual stress and plasticity are important parameters in determining crack path; their effect is modified by geometry. Furthermore, in all cases examined, the material toughness is shown to be an independent variable in determining the crack path.