Local and Global Fracture Properties in Metal Matrix Composites

The relation between the local and global values of the fracture initiation toughness is investigated for a cast Al6061-based metal matrix composite with 10% of Al2O3 particles after different heat treatments. The global values of the fracture initiation toughness are determined by conventional fracture mechanics tests. The local values of the fracture initiation toughness are found by measuring the critical crack tip opening displacement (CODi) at different locations along the crack front. To do this, an automatic fracture surface analysis system is applied. Despite of the large scatter of the individual CODi-values, a good correlation to the global fracture initiation toughness values is found.