The Physics of Fracture is the study of a driven, disordered system with many degrees of freedom. The many degrees of freedom manifests itself in that any sample of a material can respond to the driving force in a multitude of ways. Like many other similar systems (such as earthquakes, martinsitic structural phase transitions, and magnetic materials in a changing magnetic field), a brittle material can crackle when pulled apart by a tensile force. Crackling is the emission of energy in discrete avalanches of many different sizes. In studying the tensile failure of a brittle carbon foam, we observe that the process of fracture passes through stages of popping , crackling and finally snapping . Each of these stages are described by a complex statistical model which may by applied to crackling systems in general
