Overview of History

The last chapter briefly sketches the rich century-long history of fracture mechanics, with an additonal quasibrittle focus. The mainstream milestones were Griffith's 1921 introduction of energy criterion of crack propagation, Irwin's 1958 discovery of the relation of the energy release rate to the stress intensity factor of the near-tip singular stress field, Barenblatt's 1959 conception of the cohesive crack model, and Rice's 1966 discovery of the J-integral giving the energy flux into tip crack tip. Progress was spurred by the breakup of welded Liberty ships at sea and of Commet jetliners in flight, and later by many sudden shear failures of RC structures. At the interface with structural safety the main milestone was Weibull's 1939 introduction of his namesake distribution and statistical size effect in brittle failure. Hillerborg's 1976 fictitious crack model for concrete, essentially equivalent to the cohesive crack model, was a boost for computer simulation of concrete fracture. An even stronger impetus was, during 1984-1991, the gradual emergence, during 1976-87, of the crack band and nonlocal models which can capture the tensorial behavior of the FPZ, and of the energetic size effect law. Evolution of quasibrittle fracture mechanics continues until today (2020), e.g., with the recent disruption of established line-crack fracture concepts by the gap test documenting the strong effect of crack-parallel stresses. Fracture mechanics research will doubtless flourish for another century.