Crack initiation in laminated metal-intermetallic composites

Several mechanisms have been proposed to describe crack initiation and propagation in ductile-brittle composites. This experimental study shows that the failure of metal intermetallic (metal-aluminides) composites was initiated by cracking initiation in the intermetallic layers. For metal layers that allowed shear deformation, crack initiation in adjacent intermetallic layers resulted from shear bands propagating from a crack tip in the intermetallic layer through the metal layer and producing stress concentration points at the interfaces of adjacent intermetallic layers. For metal layers that did not support shear deformation, crack initiation in the intermetallic layers resulted from the continued build up of stresses within the intermetallic layers, resulting in a relatively uniform distribution of cracks within the individual intermetallic layers. Prior to failure, lateral constraints produce lateral cracks in the intermetallic layers. The final fracture features of both failure mechanisms were similar for both metal-intermetallic systems.