Micromechanics modeling of fracture

Beginning with a description of the prime mechanisms of fracture, i.e., cleavage, quasi-cleavage, intergranular cracking and microvoid coalescence, and then the crack-tip stress and strain fields which provide the driving forces to promote such fracture modes, this chapter explores the use of micromechanics to model mechanisms of fracture, beginning with the Ritchie-Knott-Rice model for stress-controlled brittle fracture and the corresponding strain-controlled model for ductile fracture. We also present the critical crack-tip opening angle model for ductile crack growth. The mechanisms for resistance to such fractures are then described in terms of the concept of intrinsic vs. extrinsic toughening, with examples given for the salient toughening mechanisms in metallic materials, ceramics, polymeric materials, and composites.