Fracture Behavior of Laminated Metal Metallic Glass Composites

The crack growth behavior of metallic glass in laminated metal-metallic glass composites was investigated and compared to the crack growth characteristics of monolithic metallic glass. The composite arrangement significantly increases the crack growth resistance of the glass. Growth in the monolithic glass is catastrophic, whereas in the composite, it is stable. The behavior is described in terms of crack growth resistance (R) curves and discussed in terms of extrinsic and intrinsic contributions to toughness. It is found that an extrinsic factor, i.e., matrix bridging, makes the major contribution to increased crack growth resistance and that a limiting crack opening displacement model interprets the experimental data quite well. Enhanced glass deformation in the crack tip region, manifested by multiple shear band formation, is responsible for the intrinsic toughening observed. Physical models are developed to estimate the level of intrinsic toughening due to this effect.