Role of controlled debonding along fiber/matrix interfaces in the strength and toughness of metal matrix composites

In metal matrix composites toughness is derived primarily from the plastic work of rupture of ductile matrix ligaments between the fractured fibers and from the plastic work of simple shear separation along steps connecting major fracture terraces. In the optimization of tensile strength in the longitudinal and transverse directions together with the respective works of fracture the most important factor is the control of the extent of debonding along interfaces between the fibers and the matrix, which develops locally in the course of deformation in a continuously changing mix of modes. In Al alloy matrix composites reinforced with Al₂O₃ fibers an effective means of controlling the key interface fracture toughness is through coarsening of Al₂Cu intermetallic interface precipitates which prescribe a ductile fracture separation layer. A combined experimental approach and micromechanical modeling, utilizing a specially tailored novel tension/shear: traction/separation law provides the means for further optimization of overall behavior. This revised version was published online in July 2006 with corrections to the Cover Date.