AN APPROACH ON THE MODE-I FRACTURE-TOUGHNESS ANISOTROPY FOR MATERIALS WITH LAYERED MICROSTRUCTURES

An approach based on the theory of fracture mechanics and in consideration of microscopic fracture events is proposed to evaluate the Mode-I fracture toughness anisotropy for materials with layered microstructures. Three mechanisms, the relative weakness of interfaces, crack path deflection and delamination toughening, are considered to contribute to the anisotropy of fracture toughness. The degree of anisotropy in fracture toughness depends on the fracture mechanisms involved. The strongest anisotropy is expected when all the three mechanisms come into effect. Using the present approach, the anisotropy of Mode-I fracture toughness for aluminium alloys with layered grain structures is evaluated. The predicted results are in agreement with those experimentally determined. The rationality of the present approach provides a way to estimate the short transverse toughness values from the in-plane toughness and the corresponding fracture behaviour.