Fracture toughness of selectively reinforced Al2124 alloy: Precrack tip in the composite side

In addition to the inherent fracture toughness of each bimaterial component, K-Q(5 pct) values of the A12124/A12124 + SiC bimaterials are largely affected by the thermal residual stresses, the elastic/plastic mismatch, and the precrack tip position. Regardless of the precrack tip distance to the interface, K-Q(5 pct) values are increased in general above "composite only" values. This is deduced to be due to the compressive residual stresses and despite the amplification of the crack driving force from the elastic/plastic mismatch. Additionally, K-Q(5 pct) values of the bimaterials increase if the precrack tip is positioned closer to the interface. When the crack propagates, it extends to the interface, bifurcates, and arrests. The load then has to be increased to promote further crack growth in the unreinforced A12124 alloy side and the subsequent onset of plastic collapse. The crack tip blunting and deflection mechanism increase the toughness attained at the onset of plastic collapse of the A12124 based bimaterials above both the composite only and "A12124 only" values.