Brittle Solids: From Physics and Chemistry to Materials Applications
Brian R. Lawn, David B. Marshall
Abstract
Hard solids with predominantly covalent–ionic bonding are finding rapidly increasing usage in many modern technologies. However, this class of solids is severely limited by their intrinsic brittleness—they break easily. It is in this context that a fundamental knowledge of brittle fracture mechanisms is of practical importance. This review covers the essential features of crack behavior in characteristically brittle solids, starting with fundamental physical and chemical models, with distinctions between equilibrium and kinetic states, stability and instability, and crack propagation and initiation. Means of imparting higher strength and toughness to otherwise brittle materials are then explored along with their pros and cons. Select technological areas where fracture properties constitute a vital facet of material function—windows and display panels, structural ceramics, biomaterials, layer structures, manufacturing, and nanomechanics—are then presented as illustrative case studies. The balance between factors such as strength and toughness, scaling and threshold effects, and crack containment and crack avoidance, as well as structure at the atomic and microstructural scales, emerge as critical factors in materials design.