An investigation of the effects of layer thickness on the fracture behavior of layered NiAI/V composites

The effect of vanadium layer thickness (100, 200 an 400 μm) on the resistance curve behavior of NiAI/V microlaminates are examined in this paper. The fracture resistance of the NiAI/V microlaminates is shown to increase with increasing layer thickness. The improved fracture toughness (compared to that of unreinforced NiAI) is associated with crack bridging and the interactions of cracks with vanadium layers. The re-initiation of cracks in adjacent NiAI layers is modeled using finite element methods. The re-inititaion is shown to occur as a result of strain concentrations at the interface between the adjacent NiAI layers. The initial deviation of the re-initiated cracks from the pure mode I direction is shown to occur in the direction of maximum shear strain. Toughening due to crack bridging is also modeled using finite element models of the observed crack/microstructure profiles.